instant lessons in chem 1

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nst nt esson

enise de VreezeKath McMicking

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erald ity ooksFirst published 1998Text Denise de Vreeze and Kath McMicking 1998Illustrations and design copyright Emerald City Books 1998This book is published by Emerald City Books as bJackline masters. The purchase price of the title reflectsthe cost of producing a small print run and the purchaser s right to make copies of the work, as describedbelow, beyond those permitted under the opyright ct 1968 as amended.The copyright owners permit the purchasing educational institution to make or authorise th e making ofcopies of the whole or part of this title provided that:1. the number of copies does not exceed the number reasonably required by the educational institution to

satisfy its teaching purposes;2 copies are only used in connection ,vith the teaching curriculum of the institution;3 copies are only made by reprographic means and not by electronic/digital means nor stored nor

transmitted;4 copies are not sold or lent;5. every copy made clearly shows the footnote: Emerald City Books 1998. This sheet may be photocopied

for non commercial classroom use.Design, formatting and diagrams by Z t t J ~ Pty LtdPrinted in Australia by Star Printery

ll further queries for copyright uses of this title should be directed to:Emerald City BooksPO Box 222St rathfield NS W 2135Australia

ISBN 1 876133 34 ]


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Instant Lessons in Chemistry ook are reproducible one or two page worksheets suitable for senior highschool Chemistry. Some of the sheets in Book 1 cover introductory chemistry topics which are prerequisitesfor courses at the senior level.The worksheets aim to give students experience in applying concepts, interpreting and presenting dataand building a core of chemistry knowledge. Ex ercises to augment English language literacy are included.The worksheets are self-contained and are designed to be done by students with minimal teacherassistance . Ea ch worksheet contains information which should be read carefully before the exercises areattempted. Answers to calculations are provided on page 48.In the contents table below, the time estimated for an average student to complete the worksheet isshown : for example, 30 indicates an average student requ ires 30 minutes to complete the worksheet.Worksheets with specific literacy exercises are further coded .

ontentsin tnoduc1:ionPhysical nd chemical propert ies .... Examples; comprehension questions on descriptive passage; word equations 120Mass nd densi ty MDefinitions and uni ts of mass, volume, density; calculations manipulating D = 3Pure substances nd mixturesFlow chart classification scheme; language exercises - points to sentences, text to pOints 1 10

_ Soli.ds l iquids nd gasesCloze passage; diagrammatic representation of Kinetic Molecular Theory of Matter; change ofstate - terminology and simple energy considerations; evaporation and boiling 1l 20

_ Soluble nd in soluble suhstancesTerminology; solubility vs temperature graphs; precipitation; solubility rules 60Dilute and concentrated. solutionsDiagrammatic representation of concentrated and dilute solutions; strong and weak acids 20Atoms and moleculesPrefixes (deci, milli, kilo, etc.); scientific notation; simple molecules - chemical formulas anddiagrammatic representation 40

The Periodic Table109 elements shown; s p d and {blocks indicated; Groups and Periods numbered; key provided

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D Th.e Periodic Table nd OlrganisatioBl of dements .Jl.8Location of periods, groups, metals, non-metals, semi-metals, transition metals; graphs: Groupdensity vs atomic number MP vs atomic number; density and MP Group IV 40lFhllme tests nd elementsWriting styles/text types (narrative, procedure and procedural recount); language features ofscientific report writing style; characteristic flame tests 1L4 O

DaUon nd ThomsonTheories of atomic st ructure - Dalton and Th om son s; calculations based on Law of ConstantProportions; properties of cathode rays and positive rays in Crookes s tube L4}@

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I N-j n @ i l : q ~ ] j l l t e alrrn@ ll"tellalil:nwte al1l:mrrnn.c mal$$Mass number; atomic n umber; isotopes; p ri nciple of mass spectro meter; calculation of re lativeatomic ma ss 3(0)A toms an d nOIDlsSimple a tomic structure; atomic number re lat ed to nu mber of p rotons; catio ns and anions relatedto Periodic Table Group; names and symbols of common iOns; ionic bond ~ j ) )R lUther f o l d


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n r t U ( m : l l l l l H [ i t O [ j ) 1 l l l

tP tr [ )P le If tU rE El Properties are th e characteristics of a substance. Different substances have different characteri stics.The properties of a substance distinguish it from other substances.o Physi al properties describe the appearance of the substance, e.g. colour, crystal shape and

measurements that can be made of the substance itself, e.g. mass of 1 cm 3 of the substance.f2 hemi l properties describe the behaviour of the substance when it is mixed with other substances,e.g. Does the substance burn? What happens to the substance with h ydrochloric acid?[ J Pure substances h ve const nt physic l nd chemic l properties. The properties of a pure substanceare always the same because the composi tion of a pure substance does not vary. Pure substances can beidentified by th eir properties.El Impure substances h ve variable properties. The properties change with the composition of th emixture.Read the following numbered paragraphs and answer the questions below.Mag nes ium - ource s, prroperth $ nd uses1 Magnesium compounds are common in the earth s crust and magnesium is estimated to account for

about 2 .1 of the total mass of the crust. Naturally occurring compounds of magnesium includemagnesium Silicate, magnesium carbonate, magnesium sulfate and magnesium chloride. Sea water is amajor source of magnesium chloride. Magnesium me tal is obtained by passing an electric currentthrough melted magnesium chloride.

2 Pure magnesium is a light-weight/low density, Silvery metal. Like other metals, it is pliable - deformingunder pressure before it breaks. I t also has the metal characteristic of being a good electrical conductor.Magnesium melts at 650C and has a boiling pOint of 1110C.

3 Oxygen in the air slowly combines with magnesium to form magnesium oxide - the normal dull greyappearance of magnesium is due to a coating of magnesium oxide. If the magnesium is heated strongly,e.g. in a flame, it combines very rapidly with the oxygen and produces an intensely bright light.Magnesium, if it is heated, also reacts with ch lorine, hydrogen or nitrogen. Magnesium does not dissolvein water but does react with steam, forming magnesium hydroxide and hydrogen gas. Hydrogen gas isalso a product of the reactions of magnesium with hydrochloric acid and sulfuric acid.The uses of magnesium are related to its properties. Its low density makes magnesium suitable for aircraftparts but it is not strong enough to be used alone. Instead , an alloy containing magnesium (90.8),aluminium 6), zinc (30,6) and manganese (0.2) is used . Similar alloys are used to make parts for highperformance cars. The aluminium increases th e strength, the zinc makes it easier to machine and th emanganese makes the part less likely to corrode. Camera flash bulbs are filled with oxygen and con taina filament made of magnesium . When an electric current passes through it, th e magnesium gets so hotit burns, emitting a flash of intense white light .

(a) Which paragraph refers to:i) the physical properties of magnesium? _ _ _ii) the chemical properties of magnesium? _iii) the occurrence of magnesium compounds 7 _ Civ how magnesium is obtained?Cv the uses of magnesium?

Cb) One characteristic of metals is malleability. 'Malleable' means a so lid lump can be flattened by beating it w itha hammer. Underline the sentence in the paragraphs above wh ich refers to magnesium being malleable.

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(c) Which words in paragraph 4 could be replaced by:(i) cut and shape using power-driven tools ?(ii) break down through reaction with substances in the environment ?(iii) long, th in coiled wire ?(iv) combines rapidly with oxygen ?

(d) List four physical properties of magnesium in point form.(i)(ii)

(ii i)(iv)

(e) Complete each of the following word equations to summarise a chemical reaction of magnesium.(i) magnesium + _ _ _ _ _ _ _ _ magnesium oxide(ii) magnesium + _ _ _ _ _ _ _ _ _ _ _ + hydrogen

magnesium + sulfuric acid magnesium sulfate +iii)(iv)v)

magnesium + magnesium chloride + _ _ magnes ium + magnesium chloride

(vi) magnesium + nitrogen _ _ (vii) + _ _ _ _ _ _ _ _ magnes ium hydride

Information about nitrog n is listed in point form below.11 combines with lithium magnesium and calcium when heatedIil colourless gasI genera lly inert/not very chemically reactivefJJ used as a safe, unreactive atmosphere during silicon chip manufacturef1 under heat and pressure combines with hydrogen lo orm ammoniaI; j obta ined by di sti lling liquid airo me lting point: - 209.S6C

boiling point: -19S .8CCl electric spark causes combination of nitrogen and oxygen to form nitric oxideQ ammonia made from nitrogen, is converted to n itric acid and used to make fertilisers and explosives(a) Rea rrange these points under the following headings:

Sourc sPhysicalprop rti s

(b) Complete the following senten ces:

hemicalprop rti s Uses

Nitrogen is a gas which is genera lly unreactive. t is a solid at temperatures less thanand a gas above . Th e of pure nitrogen is air,

from which the nitrogen is separated by fra ctiona l . Nitrogen is used to produceand from that, ferti lisers and exp losives

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assroll Mass is a measure of the amount of matter in any substance.The standard unit of mass is the kilogram kg).

Other units of mass are: microgram j.J.,g), milligram mg), gram g) and tonne t) .Volume

11 Volume is a measure of the space the ma tter occupies.The standard unit of volume is the cubic decimetre dm 3 .Other units of volume are: cubic cent imetre cm3 , cubic metre m3 , millilitre mL) and litre L).Some of these units are equivalent: for example, 1 dm 3 = 1 Land 1 cm 3 = 1 mL.

Ii Equal masses of different substances at the same temperature occupy different volumes.Reasons The particles of each substance are different and ha ve different masses.

In different substances, the space between particles may be different.El The following table conta ins examples of the volumes of 100 g masses of different substances at 25 C.

tOO 9 so id has vo ume tOO 9 iquid has vo ume tOO 9 gas has vo umeLead 8.77 mL Bromine 32.05 mL Oxygen 76405.9 mLMagnesium 57.47 mL Ethanol 127 .39 mL Ozone 50937.3 mLSodium chloride 45.46 mL Octane 143.27 mL Carbon dioxide 55567.9 mLSucrose 63.01 mL Petrol 145-152 mL Sulfur dioxide 38234.3 mL

eni tyIII ensity is a measure of the mass: volume ratio of the matter in a substance.

The symbol for density is the Greek letter p.The unit of density is grams pe r cubic centimetre g cm-3) for solids and liquids.For gases, the unit is grams per litre g L--l) .I Density values given in data books are at specified temperature and pressure - usually 25C and1Ol.3 kPa, respectiveJy. This is beca use the spa ce between particles changes with temperature andexternal pressure. Most substances expand as they get hotter.)

IiII Pure substances, composed of only one type of particle, have constant density values - at a particulartemperature and pressure, th e density is always the same.The density of an impure substance can vary, depending on the numbers of different types ofparticle present.

I l Ca lculations involving density use tIle formula: MassDensity = VolumeI Examples using figures from tIle table above are as follows:

l. MassDensity = Volume1 g... Density lead = 8.77 mL

= ] l.403 g/mL= 11.4 g/mL= 11.4 g/cm3= 11.4 g cm - 3

2. Density

: . Density carbon dio xide

MassVolume

WOg55567.9 mL

Carbon dioxide is a gas, so change the volume tolitres.:. Density carbon dioxide 100 g55.5679 L

= 1.79960 g/L= l.8 g L-1

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11

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Refer to information in the table on page 7 (see under Volume ) to answer the following questions:(a) Which substance must be impure7 Explain why.

(b) The mass of an ethanol particle is similar to the mass of an ozone particle. Give a reason for the difference inthe volumes of equal masses of these two substances. _ _

(c) The substances in the table with the lowest and the highest densities are (lowest) andhighest).

(d) Calculate the density of each of the following substances: magnesium g cm-3; ozoneg L- ; sod ium chloride g cm- 3; bromine

g cm -3; octane g cm- 3; su lfur dioxide g L- .

A sol id cylindrical plug made of pure copper has a volume of 2.75 mL. Thedensity of copper at 25C is 8.9 g cm-3 .(a) Calculate the mass of copper in the plug at 25C.(b) If the copper plug is heated to 50C, what will be the effect on each of

the following? Use increase , decrease or no change for your answer.(i) the mass of the plug:(ii) the volume of the plug:(iii) the density of the copper plug:

A bottle containing pure liquid mercury has a mass of 1.22 kg. The mass ofthe empty bottle is 200 g. At 2SOC, the density of mercury is 13.6 g cm-3Calculate the volume of mercury in the bottle at 25 C.

(a) The diagram shows layers of three pure liquids which do not dissolve ineach other. The densities of the liquids are :11 Liquid A: 1.00 g cm- 311 Liquid B:11 Liquid C:

0.66 g cm- 31.103 g cm-3

Label the liqu id layers on the diagram A, Band C.(b) Three blocks of different woods X, Y and Z are added to the container.

The densities of the wood blocks are:fi Block X:E I Block Y:

Block Z:

0.2 g cm-30 7 g cm-31.03 9 cm-3

(Wood densities are approximate because the woods are not puresubstances.)Label the diagram to show the position at which each block of woodfloats in the liquids.

mpty :2 g

With mercu ry:1 22 kg

?

-3 liquid laye rs

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D11

f8 The diagram below illustra tes on e of the ways in which matter can e classified.

Matteranythin g wh ich ta kes up space and has mass)

Pure substancesi cannot be separated by physical meansIII fixed physical and chem ical properties h ave definite composition represented by chemical formu las11 exa mples: FeS , Au, S, NaCl, Alz0 3

lements one type of atom cannot be decomposed exa mples: 0 Z P Pb, Na

Mixturess can be separated by ph ysical me ans.I no fi xed propertiesll no definite composition not represented by chemical formula sIII examples : air, soil , salt water, alloys

ompounds more than one type of atom can be decompo sedIII examples: H0, MgO, CaClz

Present the point-form information given in the above diagram by writing complete sentences. Arrange thesentences in paragraphs . Use a separate sheet of paper.Read the information below and summarise it in po in t form. Add these points to the diagram above.ill Elements can be divided into metals, semi-metals metalloids) and non -metals. Metals have a smooth

shiny appearance (a metallic lustre). They are usually solids an d all of them conduct electricity well inth solid sta te. Examples of metals are sodium, calcium, iron, copper and lead. Non -metals may besolids, liquids or gases. They do not conduct electricity well. Nitrogen, su lfur, bromine, oxygen andhydrogen are exa mples of non-m etal s.

la Compounds can be class ified as organic and inorganic. Organic compounds all contain carbon.Examples of organic compounds include methane CH4 , octane CSHl S) and et hanol CzHsOH).Inorganic compounds form when metals combine with non-metals, or when different non -metals react.So me examples are NaCl, Cu OH)z HCl and HzO.

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Use the word bank be low to complete the follow in g passage. Some words may be used more than once.gases state ethanol expanded compoundssolid gas liquid mercury non-metalwater matter most classified 25 CMatter can be according to the state in which it is found at a temperature of

_ The three states of are and_ Of the 109 e lements,

elements, the metalrema ind er of the elements exist as

occur as solids. There are twoand the bromine. The

Compounds also may be _ _ e.g. sodium chloride, sucrose, calcium sulfate) or liquids suchas _ and Gaseous include carbon dioxide, sulfurdioxide and ammon ia .

The Kinetic Molecu lar Theory of Matter says that all s made up of particles which areconstant ly moving. Their freedom to move de pe nd s on their _ and

_ are low energy or condensed states . The gaseous state is high energy orKinetic olecular Theory of atterParticles in a solid: a re constantly vibra tingI I stay in fixed positions are close to gether

Particles in a liquid: slide a round each oth er ar e close to ge th er

a) Represent the ideas above by drawing particles in the boxes.b) Which states of matter do the follow in g represent?

i) Students on chairs in a classroom:ii) Students trampolining in a gym:iii) Students walking around the room:

c) Which state of matter ha s:i) the closest particles?ii) the fastest moving particles?

hange of state

Particles in a gas are: moving fast

far apart

a) How can a so lid be changed to a liquid?b) How can a liq uid be changed to a gas7 _ _ c) How can a gas be changed to a liquid7 _ d) How can a liquid be changed to a solid 7 _ _ _

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e) In which state do the particles of any substance have:i) the highest energy? _ _ _ ii) the next lowest energy7i ii) the lowest energy? _

f) Complete the diagram below by adding the names of the changes of state.

g) How can the energy of the particles be:i) increased? ii) decreased?

Two d ssific tion systemsClassify the fol lowing substances by placing each one in the appropriate section of the table below.carbonair

SolidLquidas

calcium carbonatechlorine gas

Element

Vaporisatio 1 all1ld boiling

brominemethane gas

Compound

pure watersoil

sea water

Mixture

o A liquid can evaporate at all temperatures. Some of the particles have energy high enough to allow themto become vapour gas). As the vapour builds up above the liquid, it exerts a pressure on the liquid. Thegreater the amount of vapour the higher the vapour pressure.

D Increasing temperature en ables more particles to evaporate and the vapour pressure increases . A liquidboils when the vapour pressure becomes equal to the atmospheric pressure.

D A liquid boils at only one temperature. We can see when a liquid is boiling because of the large bubblesof vapour forming within the liquid.

The table at right shows the relationship between vapour pressureand temperature for pure water. De cide if the bo iling point ofwater usually 100C) is higher, lower or the same when:a) the atmospheric pressure s 101.3 kPa but the air

tem peratu re is 37Cb) the atmospheric pressure s 40 kPa e .g . in the high Himalaya

Mountains)c) the water is put in a pressurised container at 200 kPa

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Temperature0C)0

255075

100125150

Vapourpressure kPa)

0.63.2

12 .338 .5

101 .3232.0475.9

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D i[]OW ont:J Some substance s dis solve easily in water. We say they are soluble able to dissolve). The substance which

dissolve s is called the s lute and the substance in which it di ssolves is called the s lvent The solvent isu sually a liquid.)

Solute + Solvent = SolutionComplete the following sentences:Sug ar disso lves well in hot water. Hot water is the _ _ _ ~ ; sugar is the _ _ _ _ _ _ _ _ . Sodiumchloride disso lves in water. The name of the solute is _ _ the name of the solvent is

_ and the name of the so lution is _ _ _ i O l ~ l I l b n H t y

Iil lubility is a measure of how well a sub stan ce di ssolves . Solubility can be affected by di fferent fac tors,e.g. temp erature.

IIi Solubility of a substance is expressed as th e mass in grams which can dissolve in 100 g or 100 mL) ofwater at 25 C.

I When a substance does not di ssolve easily in water we say it is insoluble not able to dissolve). t ha s lowsolubility

The table below gives the solubilities of several inorgan ic solids at different temperatures. . indicates a value tobe filled in.)

Solid inorganicSolubility: g/ 100 g of water at ...

substance lOO 0 3 0 0 SOO 600 Aluminium sulfate 32.0 33.5 36.0 46.0 52 .0 60.0Barium hydroxide 2.0 2.5 4.0 5.6 8.2 21.0Silver nitrate 146.0 170.0 222.0 11 376.0 455 .0 525.0Potassium nitrate 17.0 21 .0 144.0 152.0 l I 168.0 176 .0Sodium chloride 35 .7 35 .8 36 .0 36 .3 I ) 37.0 37 .3Ytterbium sulfate 41.2 38.4 \ljj 21 .0 15 .8 12 .2 10.4

a) Construct a solub ili ty curve for each substance. Plot solubility on the y-axis aga in st temperature on the x-ax is,and draw a smooth curve through the points.

b) From the solubility curves, find the solub ili ties miss ing from the table above and fill in the ta b le .c) What genera lisation can you make about the effect of temperature on the solubility of most inorganic solids?

d) Calculate the pe rcentage increase in solubility between 10C and 60 C for :i) alumin ium sulfate _ ii) barium hydroxide _ iii) silver nitrate _ iv) potassium nitratev) sodium chloride _ _ vi) ytterb ium sulfate

e) For the substan ces listed in the table, temperature has:i) the greatest effect on the solub ility of _ _ _ ii) the least effect on the solubility of _ _ _

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The following tab le gives the solubilities of several gases at different temperatures . The solubil ity of all gasesincreases with pressure. The solubilities in the table are at a constant pressure of 101.3 kPa.)

SoLubility of gases: mg/ l g of water at ..as soe lOoe 0e 3 0e 4 0e sooe 600

Nitrogen 2.60 2.30 1.90 1.60 1.40 1.20 1.10Oxygen 6.10 5.40 4.30 3.60 3.10 2.70 2.30Hydrogen 0.18 0.17 0.16 0.15 0.14 0.13 0.12Carbon dioxide 277.40 231.80 168 .80 125.70 97 .30 76.10 57 .60Nitric oxide 8.60 7.50 6.20 5.20 4.40 3.80 3.20

a) From the data, what can you say about the general effect of temperature on the solubi l ty of gases?

b) Calculate:(i) the maximum mass of oxygen which will dissolve in 1 L of water at 10C;(ii) the volume of this mass of oxygen density of oxygen at 10C = 1.4290 g L- l) .

PreEipit ating When solutions of two soluble salts are mixed, they sometimes form an insoluble salt. This insoluble salt

appears as a cloudiness and, as it thickens, it often falls to the bottom of the test tube. I t is then calleda precipitate. Salts are chemical compounds made from acids, e.g. sulfates, chlorides, nitrates,carbonates and acetates are salts .) For example, when solutions of sodium chloride and silver nitrate aremixed, a precipitate of silver chloride forms. The silver chloride appears as a cloudiness or precipitatebecause it has a low solubility in water.

sodium chloride solution silver nitrate solution 7 sodium nitrate solution silver chloride precipitateSolubility at 20C: 36 g/lOO g 222 g/lOO g 88 g/100 g 1.5 x 10-4 g/100 g

Solubil i ty rules or common altNote: TIle rules must be applied in order : Rule 1, then Rule 2, etc.are said to be insoluble. Substances

with solubilities 10- 1 g/100 g1234)

Sodium Na -'), potassium (K ) and ammonium NB;; salts are so lu leNitrates and acetates are so lu leSilver (Ag l ), lead mercury Hg ) and copper Cu l ) compounds are inso lubleChlorides, bromides and iodides are so lu le except for copper iodide.Carbonates, sulfides, oxides and h ydroxides are insolubleSulfates except ca lcium sulfate an d barium sulfate are so lu le

Draw a box around the insoluble salt in each of the following word equations:a) lead nitrate potass ium iodide 7 lead iodide potassium nitrateb) sodium sulfate ..l-. barium chloride 7 sod ium chloride barium sulfatec) sodium sulf ide magneSium nitrate 7 magnesium sulfide , sodium nitrated) ammonium chloride silver nitrate 7 silver chloride ammon ium nitratee) copper sulfate sodium carbonate 7 copper carbonate sodium su l ate

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r g rlli @Hm [j] cc: ern trn tr: ITTI 11: rr@tft D]DJ t ~

tll ilute solutions contain a small amount of solute relative to the amount of solvent.For examp le, 0.01 g of potassium nitrate dissolved in 1 L of water is a very dilu te solution .f.i oncentrated solut ions contain a large amount of solute relative to the solvent vo lu me .

For example, 300 g of sugar dissolved in 100 g of water is a concentrated sugar solu tion.Draw diagrams representing di lute and concentrated solutions . Use to represent a solvent particle and 0 torepresent a solute particle.(a) In the box labe lled Dilute solution draw 3 solute particles and 20 solvent part icles.(b) In the box labelled Concentrated solution draw 20 solute particles and 10 solvent particles.

Dilute solut on oncentrated solut on

Cl turated solutions are so concentrated that they contain as much solute as the solvent will hold . Theonly way to make more solu te di ssolve is to increase the temperature (assuming the solubility of thesolute increases with temperature) .

[3 In chemistry the terms strong and weak are used to de scribe acids and do not mean concentrated anddilute .

I;: The particles of an acid break up to release hydrogen ions (H+ ion s) : HA (acid) ---7 H+ + A- .- trong iI u id

III Most of the acid particles break up and lots of hydrogen ions are released .ill For example, hydrochloric acid, nitric acid and suJfuric acid are strong acids .a Strong acids are very corrosive .iI 0.365 g of h ydrochloric acid dissolved in 1 L of water is a dilute solution of a strong acid .:II 36 5 g of hydrochloric acid dissolved in 1 L of water is a concen trated solution of a strong acid.

eak dlr idr;J Only a few of the acid particles break up and only a few hydrogen ions are released.Ell For example, hydrofluoric aCid, acetic acid, citr ic acid and lactic acid are weak acids.Il:l Weak acids are not very corrosive; many occur naturally in foodstuffs .l 0 .02 g of hyclrofluoric acid dissolved in 1 L of water is a dilu te so lu tion of a weak acid.

13 200 g of hydrofluoric acid dissolved in 1 L of water is a concentrated solution of a weak acid.The dots in these diagrams represent water molecules. Decide whether each of the followin g are: i) concentratedor dilute solutions; (ii) strong or wea k acids.

0 (a)o Q

oV (i)0 (ii):8: 0 0 0 e 0 ~ ~

o f/?\. 8 MA- 008::8 0 ~ o ii). .00: : 8 0.8 0 0 0

(c)Ciii)

(d)(i)(i i)

Refer to the solubility va lues on page 12 to classify each of the fo llowing as dilute , concentrated or saturated .Ca) 22 0 g of silver ni trate in 100 mL of water at 20 C ______(b) 109 sodium chloride in 10 mL of wate r at 20 C ______(c) 0.005 g of alum iniu m su lfate in 1 L of wate r at 20 C ______

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ftoms

D

rn Atoms are the building blocks of matter. All substances are made of atoms in some sort of arrangement.There are 109 different kinds of atom. Differen ces between substances are caused by differences in theiratoms and in the way the atoms are combined.

JI Atoms are extremely small, about one ten millionth of a millimetre in diameter. A helium gas birthdayballoon contains about 400000000000000000000000 helium atoms.

(a) Write the number of helium atoms given above in scientific notation form .(b) The diameter of a sodium atom is 3.12 x 10-4 j Lm j.Lm is the abbreviation of micrometre ). Calculate thisdiameter in metres. Express your answer in scientific notation.(c) The diameter of a silicon atom is 0.234 nanometres (nm). What is the diameter in metres?(d) The diameter of a ch lo rine atom is 1.98 x 10 2 picometres (pm). Calculate the equivalent number of metres,

expressed in scientific notation .(e) Angstrom unit N ) is another unit used to measure very small distances.

10 N = 1 nm: . 1 N = m

f) Complete the following Ratio of Atom Diameters:sodium: silicon: chlorine = 1

(g) Using an electron microscope (magnificat ion 2 000 000), the diameter of barium atoms was measured as4 x 10- 10 m. Convert this to nanometres.

Information for ExercisePrefixes and powers o 1

] = 10Larger than onegiga(G) = 109 = 1 000000000mega(M) = 106 = 1 000000kilo = 103 = 1000

Scientific notation

Smaller than onedeci = 10- 1 = _1_10. 10 0 1centl = lOO

milli = 10 -3 = _ _1000micro(j.L) = ] 0-6 = 1. 1000000nano = 10 - 9 = 11000000000pi co = 10- 1 2

Numbers are shown as one unit pl us dec imals multipli ed by a power of 10, e.g. 1142 is written as1.142 x 103, 0.03456 is written as 3.456 x 10 -2 .

Molecule A molecule is a group of atoms. Two or more atoms can join together to make a molecule. In molecules

of an element all the atoms are the same. In a molecule of a compound different types of atoms arecombined. Millions of different molecules can be made from different combinations of the 109 differenttypes of atoms .

11 For many substances, the chemical formula represents one molecule of th e substance, e.g. th e formul ae l2 indicates th at there are two chlorine atoms combined in each mol ecule of chlorine. H20 theformula for water, shows that in one water molecule, there are two hydrogen atoms combined with oneoxygen atom .

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a) Cla ss ify each of t he following diagrams as representing either separate atoms or mo lecules.

i) ii) iii) iv) v)

b) Complete the following table using the key:Hydrogen atom e N;tcogen atom, @ Oxyg en atom, C

IOJ5lvi)

Molecule name Formula Molecule diagram ELement or compoundNitrogen Nz

Hydrogen H2

Oxygen Oz

Ozone 03

Water HzOhydrogen oxide)Ammonia NH3nitrogen hydride)

Nitrous oxide NzO

Nitric oxide NO

c) Next to the formu las for eac h of the fol lowing molecular compounds, write the name and number of ea chtype of atom combined to make the molecu le The f irst one has been done as an example.i) sulfur diox ide 2 1 sulfur atom and 2 oxygen atomsii) hydrogen bromide HBriii) glucose C6 H120 6iv) methane CH 4v) oxygen ch lo ride OCI2vi) nitrogen fluoride NF 3vii) phosphorus iodide P 3

Emerald City Books 1998. This sheet may be photocopied for non-commercial classroom use . 6


17/49

6)en3' :co00,.;-en>-'-0-0?-1

en=rro3'erro0:::s-oSn0

~ .roD..-.,: : l0=;n033nn

3035ico

>-- . J

0C

I 4

IIb l o e

H1.008

Hydrogen

3 4li Be6.941 9.012llthlUm Beryllium

11 12Na Mg

22.99 24.31Sodium Magnesium19 20K Ca39 .10 40.08Potassium CalCIUm37 38Rb Sr85.1 7 87.62Rubidium Strontium

55 56Cs Ba132.9 137.3Cesium Barium

87 88Fr Ra(223) ( 226 )Francium Radium

21Sc

44.96Scandium39 Y

88 .91Yttflum

57la

138.9Lanthanum89 ..Ac(2 27)Actlnium

KeyAtomI c number 79 All Symbol of elementAtomic mass 197 .0

Gold Name of element

d-block

22 23 24 25 26Ti V Cr Mn Fe47.90 50 .94 52 .00 54 94 55.85TItanium VanadIum Chromium f.langanese I ron

40 41 42 4 3 4/lr Nb Mo Te Ru

91.22 92 .91 95.94 98 .91 101.1Zirconium N l blUlll r-Iolybdenum Technetium Ruthenium

72 73 74 75 76Hf Ta W Re Os178.5 180.9 183.9 186 .2 190.2a f n i u m Tantalum Tungsten Rhenium Osmium

104 105 106 107 108Db JI Rf Bh Hn(261 ) (262 ) (2 63 ) (262 ) (265 )Dubmum Joliot iu m Rutherfordium Bohnurn Hahnium

58 59 60 61 62Ce Pr Nd Pm Sm140 . 1 140.9 144 .2 (147) 150 .4Ce rium Praseodymium Neodym iu m Promethium Sama rium

9C 91 92 93 94Th Pa U Np Pu232 .0 (231) 238.1 (237) (242)lhor ium Protactil1lllm Uran ium Neptunium Plutonium

- - - --

Group Number III IV V VI VII VIII

He4.003Helium ~m illdF9

p-block Wl5 6 7 8 9 10B C N 0 F Ne10.81 12.01 14.01 16.00 19.00 20.18 mc;3Boron Carbon N t logen Oxygen rtuorine Neon Q;;lD13 14 15 16 17 18

AI Si P S Cl Ar26.98 28.09 30.97 32 .0 6 35.45 39 .95. Phosphorus Sulfur Chlorine Argonlumlll1urn Silicon 9c z o

27 28 29 30 31 32 33 34 35 36Co Ni Cu Zn Ga Ge As Se Br Kr A58 .93 58 .71 63.55 65.38 69 .72 72.59 74.92 78 .96 79.90 83.80

Cobalt Nickel OPPPT Zinc Gallium GermanlUm ArseniC Selenium Bromine Krypton45 1 6 47 48 49 50 51 52 53 54

Rh Pd Ag Cd In Sn Sb Te I Xe102 .9 106.4 107.9 112.4 11/,.8 118.7 121.8 127 .6 126 .9 131 .3RhodIUm PalladIum Sl iver Cadmium lodium TUI Antimony Tellunum Iodine Xenon

~o;::n

77 78 79 80 81 82 83 84 85 86Ir Pt All Hg Tt Pb Bi Po At Rn u @192.2 195 .1 197.0 200.6 204.4 207.2 209 .0 (210) (210 ) (222 )Iridium Plat 1Ilum Gold l-lercul / Ih aUlul l L e ~ d Bismuth Polonium Astatine Radon

109Mt(266 )Mei tnelium

f-bloc k

63 64 65 66 67 68 69 70 71Eu Gd Tb Dy Ho Er Tm Yb lu152.0 157.3 158 .9 162.5 164.9 167. 3 168.9 173 .0 175 .0Europium Gadolinium TerblUffi Dy sprosium Holmlllm Erbium Thulium Ytterbium lutetium

95 96 97 98 99 100 101 102 103Am Cm Bk cr Es Fm Md No Lr( 243 ) (247) (24 5) (251 ) 25 / ) ( 253) (256) (254 ) (257)Amer iclUm Curium Berkelium ( alifol r IUm Einsteinium Fermium Mendelevluffi Nobelium lawrencium


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f l h l ~ f P l ~ r g r n m ~mOO o

The layout of the fun Periodic Table is shown below.Periods 1 0 He2

34567

Li BeISe

Transition MetalsTi

I La nth no dsActir oids J I

B C N 0 F NetV Cr Mn Fe Co Ni Cu Zn

Normal Periodic TableThe Periodic Table is usually in the shorter form shown on page 17.Periods

Deriods are the rows of the Periodic Table. The elements are arranged in order of increasing atomic

number (number of protons in each atom s nucleus) across each Period. This is also roughly the order ofincreasing atomic mass.

Complete the following table:Number of elementsPeriod in the Period First element Last element

1 22 Neon345 Rubidium67 3 Meitnerium

Groups

11

11

roups are the eight main columns. The Group s are usually numbered I VlII using Roman numerals. Theelements in each group have similar properties.

El Group I (alkali metals) begins with the m etal lithium. Hydrogen has some chemical properties similarto these metals but because it is a gas it is shown sepa ratel y.

EiI Group VII (halogens) comprises very chemically reactive no n-metals .SI Group VIII (noble gases) contains gases which arc inert (unreactive). These gases are the only elements

in which the particles are discrete atoms (separate atoms).True or false7Ca Sodium and sulfur have simi lar properties.Cb Fluorine is chemically similar to chlorine.Cc A helium balloon contains helium molecules.Cd Light g lobes are filled with argon because it does not react with the hot metal filament.e) Calcium reacts the same way as magnes ium does in many chemical reactions.J The zig-zag line in the Periodic Table separates metals from non-metals. Metals are on the left of the

line and non-metals are on the right. Elements close to th e line are semi-metals and have both metaland non-metal characteristics.

Classify the fol lowing elements as metals, semi-metals, or non-metals:argon arsenic boron bromine germanium goldsilicon silver sodium sulfur tellurium titan iumii Transition metals make up the block in the middle of the table . Many transition me tal s are used in

industry. Compounds of transition metals are often coloured. Emerald City Books 1998. This sheet may be photocopied for non-commercial classroom use. 18


19/49

rrglj][Jir ti l r ~ . ~ llJtluBa ' ~ a t f l , n tmf f e ~ H m ~

Name a trans ition metal wh ich is used :Ca) as the main component of steelCb) in electrical wiring because of its high conduct ivityCc in drill bits and light globe fi laments because of its hardness and high melting point _ Cd) to make batteries, corrosion-resistant roofing and alloys, e.g. brass(e) where light weight and strength are important, e.g. in spacecraft and artificial joints _ _ _Physical properties Group I

Atomic no . Z) Element Density g cm-3) Melting point 0C) Boiling point (0C3 Li 0.53 180 1342

11 Na 0.97 98 88319 K 0.86 63 76037 Rb 1. 53 39 68655 Cs 1.88 28 66987 Fr ? ? ?

Francium is a rare, radioactive element isolated in 1939 by Marguerite Perey, who named it after her nativecountry, France. The density, melting point (MP) and boiling point BP) of francium can be predicted fromthe trend in these values for the other elements in roup 1.Ca) Using graph paper, plot MP aga ins t atom ic number for the Group I elements. Draw a smooth curve through

the points. Extrapolate the curve to find a value for MP at atomic number 87.i) Estimated MP of francium = Cii) Write a sentence describing the trend in melting points shown by your graph .

(b) On another sheet of graph paper, plot density value against atomic number for the same elements. Draw asmooth curve which best fits the points. Extrapolate the curve to estimate a value for the density of francium.(Include the unit of density in your answer.)

Estimated density of francium =Physical properties Group IV

Atomic no .6

143250

82

ElementCarbonIil diamond allotropeIII graphite allotropeEl fullerene allotropesSiliconGe rman iumTinEl white allotropern grey allotropeLead

Density g cm -3 ) Melting point (QC

2.25 All allotropes sublime;3.51 diamond and graphite

approx. 1.50 sublime at about 4000 C2.33 14205.35 9457.28 2325.79

Grey changes to white bove 13 C11.34 327(a) i) Complete the following sentence: are different forms of the same element resulting

from different arrangements of the element s atoms.ii) In the data g iven above, what evidence is there that carbon atoms are arra nged differently in diamond

and graphite? _ _ (b) Is there a definite trend in MP in Group IV? Expla in.

Emerald Cty Books 1998. This sheet may be photocopied for non-commercia l classroom use. 19


20/49

ext i type = tty e lJlf WIr t Oll Jg]g The style in which you write something depends on why you are writing it. For example, a letter to yourgrandmother to tell her about your last school holidays is in a different style from a letter to the PoliceDepartment to object to a parking fine . Different styles have different language features - sentencelength, word order w ithin a sentence, etc.

Nlll "lrillit6ve text \typeThe following passage is an example of narrative style. The writer is telling a story about the flame testexperiment to a friend.

We ll, I lit the bunsen, then I dipped a piece of clean platinum wire into some barium chloride. I held thewire in the flame and noticed a co lour like ripe Granny Smith apples. 1 cleaned the wire then Ken gaveme some ca lcium chloride. This time the flam e turned an orangey red co lour After this it was Kim s turn .She heated some strontium chloride Thi s turned the flam e a beautiful bright rose pink . W hen she usedpotassium ch loride the flam e turned a sort of lilac or light purple I got to do the copper chloride Itchanged Ihe flam e not to blue but to green. The last one we did was sodium chloride The flame turneda de ep bright yellow

rocedure text typell This style of writing is used for the instructions for an experiment and is set ou t under the headings Aim

Equipm ent and Method as shown in the following example .Aim: To find the temperature of boiling water.fqu ip rnent: bu nsen burner, tripod, wire gauze, beaker, thermometer.Method: 1. Fill the beaker with water.2. Place the beaker on tripod and wire gauze.

3. Light the bunsen burner.4. Heat the water until it boils.5. Measure the temperature of the boiling water.6. Record the temperature of the boiling water.

The A im sec tion specifies the goal or purpose of the experim en t . Un der th is heading you write what youare trying to do in the experiment. The section usu ally starts 'To observe ... , 'To measure .. , 'To find . .etc.The Equipment section lists the equipment you need in the experiment.

Id The Method sec t"ion comprises the instructions for doing the experiment written in step form . The stepsare often numbered.In the above exampl e of procedure text type, notice the language features:1. Co mmands - Do this l , Do that2. The verb or action word is often firs t in the sentence.3. Se ntences are short.

Read the example of narrat ive style again . Is the language scientific7 YES/NOWhat features make you say this?From in formation in the student's story, write the instruct ions for the flame test experiment in the style ofprocedure text type. Use the heading s: Aim Equipment and Method Use numbered steps and commands for theMethod section.

Emerald i ty Boo ks 1998. This sheet may be photocopied fo r non -commercial classroom use. 20


21/49

? l r o < r . : ~ d u r r < i ' 8 ~ We:


22/49

D

ll John Dalton 1766- 1844) is famou s for hi s theory, published in 1803, that all matter is made up of tiny,indivisible a toms. The theory wa s b ased on his own experiments and those of other 17th and 18thcentury scientists. Two main types of experimen ts were used to develop Dalton's theory of a tomicstructure .1. ompressibi /i t l of gases This could be explained i f th e gases were composed of wid ely-separa ted

particles; when pressure was applied to the gas , the particles were squeeze d clo ser together.

p { > z z z z z z z z . . . J ~ _ ...Il 2 Y P V Z z,.... 0 : :Ro be rt BoyLe in 1662 fou nd th at if t he pre ss ur e dou bLed , t he voL ume of t he ga s haLved

2. Th e constant whole number mass ratio of elem ents in a compound e.g. in any amount of copper ox ide,m ass of copper m ass of oxygen = 4:]. The fact th at th e mass ratio in cop per oxide wa s always 4:1suggested that di screte atoms of copper and oxy gen combined . A po ssib le explan ation of the rat iowa s that each copper atom wa s four times th e ma ss of each oxygen atom.

Joseph Lou is Proust showed in 1799 that copper carbonate aLways contained copper, oxyg en a nd carbon i n t he ratio 5:4:1ll Law of Constant Proportions: the mass ratio of elements combined in a compound is constant .In copper carbona te , the mass rat io copper: oxygen : carbon = 5:4:1.a) A sample of copper carbonate contains 77 9 of copper, 15.4 g of carbon and 61 6 9 of oxygen . Confirm themass ratio Cu : 0 : C in the samp le .b) What fraction of the mass of copper carbonate is due to:

i) the coppe r7 _ _ _ _ii) the oxygen? _ _ _ _i ii ) the carbon 7 _

c) How many grams of oxygen are combined with carb on and copper) to make 120 g of co pper carbonate7d) Cal culate the maximum mass of copper carbon ate which could be made from 20 g of copper.e) How many grams of carbon are needed to combine with 7 g of coppe r to make copper carbonate?

The percentage composition by mas s of the binary compound, carbon fluor ide, is 13 .64 carbon and 86.3 6fluorine measured to two decimal places only). Calculate the simplest whole number ratio for mass carbon : massfluorine in carbon fluoride .Sodium forms two different compounds with oxygen: sod ium ox ide and sodium peroxide .In sodium oxide, mass sodium : mass oxyg en = 23:8.In sodium peroxide, mass sodium : mass oxygen = 23 :1 6.From these mass rat ios,numbe r of oxygen atoms in sodium oxide: number of oxygen atoms in sod ium peroxide = _ _ :_ _ .

Emerald Cty Books 19 98. This sheet may be ph oto copied for no n-commercial classroom use . 22


23/49

Sir h] eph ThomslD ll.l

I t

Sir ]oseph Thomson (1856-1940) earned the Nobel Prize in physics in 1906 for his work on electrons.He proved conclusively that cathode rays were streams of negatively charged particles, for which he usedthe term electrons . Most importantly, Thomson showed that the mass of an electron must be much lessthan that of a hydrogen atom; this indicated that electrons were subatomic particle s.

glass t ube'no / E .-- -:- \ cathodde ~ ca th ode rays. 1 EO

e

\,. E :.J: 1111 hig h vo lta ge

I l Cathode rays and positive rays were both madeof charged particles.

BI The positive and negative particles came fromthe atoms of gas at low pressure inside theCrookes tube (cathode ray tube) .

Ii i Thomson developed a model of an atom toexplain the existen ce of positive and negativecharged particles within atoms.

Cathode rays cause a fluorescent glow when they hitthe glass wall of the Crookes tube . The following setups are used to demonstrate some other properties ofcathode rays .(a) Which set-up provides ev id en ce that:

(i) cathode rays travel in stra ight lines?(ii) cathode rays are negatively charged?(iii) cathode rays are made up of particles?(iv) cathode rays are deflected by an electric

field?(b) Complete the following sentences (one word foreach line space):

Cathode rays cause a whenthey str ike the glass wall of the Crookes tube.When a solid object is placedthe cathode and the glass, a _ _forms on the glass. Because this happens thecathode rays must

gas atlow pressureinside

sph ere ofpositivecha rge s

positivecha rge s

glas s tube/~ < E ~ I )cathode rays I positive rays~ < E ~ - - - ~ - - : )~ E O ~ - - - - - - - - - - - ) 7

high voltage ca th ode

negativeelectronsembedded

much largerthan elect rons

equalnumbersof positivesand negativesThis model is often called the plum pudding model .A plum pudding is a sort of fruit cake. RaiSins,cherries, ete. are embedded in the ball-shaped cake.

A

anode+

Banode

c

cross-shapedshadow metal cross

rollingpaddle wheel

_ cathode

_ cathode

positivelycharged platef ~ c = = = = : : ~ ~ = : ; - ~ cat hod e

11 In Thomson s plum pudding model of the atom: negativelycharged plate(a) which components are compared to the fruit of a plum pudding? _ _ (b) why is the atom electrically neutral/uncharged? _

Emerald City Books 1998. This sheet may be photocopied for non-commercial classroom use . 23


24/49

D

o t ~ ~ ~ @ ~ . r ~ m @ 1 l r t g W ~ @ 3 t t [ J ~ i l l G C

m The m ss num er A) of an atom is th e totalnumber of protons and n eutrons contained inthe nucleus of the atom.

IiII The atomic num er Z) is the number ofprotons only.

n u ~ b ~ ~ 23. ELEMENT e.g. a

tomlCnumberNum ber of neutrons in an atom = Mass number - Atom ic n um ber

Comple te the following table:ement atom Symbol o of protons o of neutrons

Helium H eSodi um 23NaOxygen 6 08Pho sph orus 3 p1SCop pe r 63 CU29Iodine 27 I53

Isotopes ar e different atom s of the sam e element which have different numbers of neutrons but the samenumber of proton s in the nucleus.

III Ma n y elements ha ve naturally occurr ing isotopes. Isotopes can be made artificially by bombardingatoms of the elemen t with n eutron s. Examples of isotopes: l. Isotopes of hydrogen: 2. Isotopes of carbon:

- pronounced 'Hydrogen lH - Hydrogen 2 deuterium)H - Hydrogen 3 (tritium)

l2 C - Carbon 126J3c - Carbon 136l C - Ca rbon 14

Ca) What do a ll three isotopes of hydrogen have in common?Cb) What difference is there in the atomic structure of hydrogen, de uter ium and tritium?

Cc) How many protons are there in the nucleus of every carbon atom? _ _Cd) The most common isotope of carbon has 6 neutrons. What is its ma ss numbe r? _ _ _

Atomic mass Al mos t all th e mass of an atom is in it s nucleus. A neutron has very nearly the same mass as the mass

of a proton . Electrons have al most zero mass.The rea l mass of a proton is l.673 x 10- 24 g and of an electron, 9 .110 x 10 - 28 g. Atom s are too sm all tobe \,veighed eas il y.

elat ive atomic mass

1111 Relative atomic m A,) is the m ass of an a tom compared with a standard atom. The relat ive atomic mass

value of sodium is 23 : a sodium atom is 23 times heavier than the lightest hydrogen atom iH) which hasa relative atomic mass value of 1. The mo dern standa rd atom is the C isotope which has a value of 12.

Given that a proton and a neutron each have a mass value of 1, what is the rel at ive atomic mass of:Ca) the isotope? Cc) an atom which has mass number 9? ______ _Cb) an atom containing 4 neutron s and Cd) the deuterium isotope? ______

13 protons? __ Ce) 34 S ?16 . Emerald City Boo ks 1998. This sheet may be photocopie d for non -commercial classroom use. 24


25/49

j1] t [ill cm Em IDR El @J t[0 @rft ern rTIrn0 r [cent ]

a IrBl lg] ( E R ~ / t E a t Ol m h: m a

I t

Iil The m ss sp trom t r is the instrument used to separate different atoms and measure their relativeatomic masses. The instrument actually compares the masses of io ns wh ich have one positive charge ,e.g. Ne . This is effectively the same as comparing atomic masses because losing an electron makes verylittle di fference to the mass.

(3) mag neti cfi eld / - - - - : >

CD dete ctor

- -

ICB meta l platewith slit

vaporisedsample +injectio npoin t

-


26/49

B The str uct ure showing main subat omicparticles is shown in the diagram below:

( )

o Th e central nucleus is on ly about 1/1 0 000 of theatom s diameter.

Eil The nucleus contains:

Q

nucleus p rotons andneutrons )electrons

protons - positive particles (symbol p+)neutrons - neutral particles (symbol n)

ill The space around th e nucleus is occupied by fasimoving electrons - negative charges (symbol e- ).

l In any complete atom the number of positiveprotons is balanced by an equal number ofnegative electrons. A complete atom is electricallyneutral.

Ii l Th e tomic number Z) of an element is th e numberofprotons in its nucleus. For example, a hydrogenatom ha s 1 proton, a chlorine atom h as 17 protonsand a uranium atom has 92 protons.

D Use the Periodic Table on page 17 to complete the following table:

ons

Element atomSymbolNo. of p'"No. of e -

19Co pper Chlo rine

Ca

8

m l ll s are charged par ticles . When atoms gain or lo se electrons they change into ions. Extra electronschange a neutra l atom into a n egative ion. Losing elec trons changes a neutral a tom into a positi ve io n.The number of protons in the nucleus do es no t change when ions form .

III Positive ions (cations) form when metal atoms lose electrons. A complete atom h as an equal numberof protons and electrons. The positive charge is caused by the number of protons exceeding the numberof elect rons remaining. Th e name of a metal ion is th e same as th e name of th e metal atom.

ill Negative ions (anions) form when non -metal atoms gain electrons. The n egative charge is camed byth e number of elec tron s exceeding the number of protons. The names of non-metal ions end in ide ' ,e.g . chloride ion .

W Genera l guide to the number of electrons lost or gained by atoms which form ions:1. Group I metals lose 1 e- ; 4 . Group VI non-metals ga in 2 e- ;ions have a sin gle po si tive cba rge, e.g. K+. ions bave two n ega tiv e charges, e.g. 0 2 - .

2. Group II metals lo se 2 e- ; 5. Group VII non-metals gain 1 e- ;ions ha ve two po si ti ve charges, c.g Ca 2+ . ions h ave a si ngl e negative charge, e.g. Cl .

3. Group III metals lose 3 e- ;ions bave three positive cbarges, e.g . AP - .

(Th ere is no gen era l rule for the charge on ions formed from atom s o f Groups IV and V. Atoms of Grou pVIII elem ents do not form ion s or combine with other atoms in any way.)

11 Complete the table. IonNa+Ca 2+A13F-02-Zn2+

No. of p

Emerald Ci ty Books 1998. This sheet may be photoco pied for non -commercial classroom use.

No. of e-

26


27/49

DD C D i l D ~ [[ []DlJlt]

Complete the fo llowin g tables of ion names and symbols:Metal ion cation) Sodium Caesium Calcium StrontiumSymbol

Non-metal ion anion) Oxid e ChlorideSymbol S2- Cl- 1-

[]thetr l Omm OI l l met:aD iO l13 As well as the metals in Groups I II and Ill, many common metals are located in the transition metal

block of the Periodic Table. Tin and lead, at the bottom of Group IV are also widely used. Commonmetal ions not included in the table above are listed below. Some metals can form more than one ion.Roman numerals are included in the names of these ions to indicate the number of positive charges onthe ion.

Complete the names miss ing from the table below:

Ion name SymbolC02

Coba lt Ill) C0 3+Cu +

Copper II) Cu 2+Gold 1) Au+

Au 3+Fe2+

lonh: bond

Ion nameIron Ill)Ti n II)Me rcury II)Nc kelSilverZinc

SymbolFe3+Pb 2+Sn 2+Hg 2Ni 2+AgZn 2+

rn In any chemical reaction, bonds are formed between atoms. Only the electrons of the atoms are in volvedin joining the atoms; the nucleus is unaffected.Ell Generally when metals combine with no n-metals, each non-metal atom pulls a particular number ofelectrons from the metal atom. This creates negative and positive ions.m Once the positive and negative ions have formed, they are held together by an ionic bond - the strongelectros tatic attraction between ions with opposite charges.Complete the table below. Name the toms which have combined by ionic bonding to form each of thecompounds . Name and write symbols for the positi ve and negative ions in the compound

Atoms combining Ionic compoundSodium brom ideLead II) iodidePotassi um su lfideCalcium flu orideBarium chlori deGo ld ) oxideIron Ill) oxide

Positive ionname , symbol)

Eme rald Ci ty Books 1998 . This sheet may be photocopied for non-commercial classroom use .

Negative ionname, symbol)

27


28/49

11

l l Before the experiments of Geiger and Marsden and their interpretation by Rutherford, the acceptedmod el of the atom was]. ]. Thomson s plum pudding . This considered the atom to be a sphere ofpositive charge in which negatively charged electrons were embedded.

Ilil Rutherford and his colleagues used the radioactive element plutonium as a source of fast-moving alphaparticles. a particles are positively charged and equivalent to a e nucleus.) They fired the alphaparticles at thin gold foil. A movab le screen was used to detect alpha particles emerging from the target.This screen was painted with a substance which gave off light when an alpha particle hit it .

J The observations were:1 most alpha particles passed straight through the gold foil or were deflected only slightly;2. some alpha particles bounced right back towards the source.

Use source, gold fo il , most a part icles and occasional a particles to label the fo ll owing diagram:

movabledete ctor

ev acuat ed

ll in the spaces in the following sentences (one word in each space):Observation1 Most x particles passed straight through.

2. Some positive particles were thrown stra ightback.

onclusion1. The massive part of the atom is very

2. The charge on the smal l dense part of the atomis

Rutherford deduced that atoms consisted of a dense core wh ich we call theSurround ing the nucleus is a cloud of tiny partic les, the electrons . As the

electrons were thought to be circling the , they were accelerating (veloc ity constantlychanging). According to classical electrodynamic theory, they should be emitting energy so would eventuallysp iral into the _

D Emerald Cty Books 1998. Thi s sheet may be photocopied for non-commercial class room use. 28


29/49

l ~ e m B[llti1ltr

n

In 1913 Niels Bohr proposed that:il electrons move in circular orbits arou nd the n ucleus;f l electrons radiate no energy while in these orbits;] electrons ex ist on ly in fixed energy levels; each orbit is a particular energy level;iI when an ele ctron moves from one orbit to another of higher energy, a quantum (packet) of energy is

absorbed;IiiI when an electron moves from one orbit to another of lower energy, a quantum of energy is released;Gl the value of the quantum of en e rgy absorbed or released is the djfference in va lue between th e two

energy levels.Answer each of the following questions:(a) i) Who devised the plum pudding model of the atom? _

ii) Where were the electrons in the plum pudding model? _ _ (b) i) Who performed experiments which led to the improvement of the p lum pudd ing model? _ _ _

i i) In these experiments, what sort of particles were used?iii) What was the source of these particles?iv) What are the properties of these particles?

(v) In the experiments, at which particular material were the particles fired?vi) Why might that particular material have been used?

(vii) In the experiments, how were the particles detected? _ _viii) After the experimental results were ana lysed, what new model of atomic structure was devised?

(ix) What was wron g with this new model of atomic structure? _ (c) i) When did Bohr propose an even better model of atomic structure?

ii) Use a diagram to ou tline the Bohr model of atomic structure.

Refer to Flame tests and elements on pa ge 20. Write up the work of Rutherford, Geiger and Marsden as a modernschool expe riment. Use the procedural recount style of writing, e.g. include a goal (e .g. Aim : To ... ), th e materialused (e.g . Equ ipment: .. . , a method written in passive voice (e.g. a particles were fired at .. . ), resu lts andconclusion.

Emerald Cty Books 1998. This sheet may be photocopied for non-commercial classroom use . 29


30/49

Ifl r [ f Ga] fflJ . m ErnLt fm fli IJi

Cl The electrons moving in the space around the nucleus of an atom occupy differen t energy levels . Thisidea is simplified in diagrams which show the electrons in orbits around the nucleus. The energy levelsare called shells and are numbered from the nucleus outwards. Shell No. 1 is the lowest energy level.

Example: lithium atom Example: Neon atomnucleus

3 protons and4 neutrons Shell No. 10 protons and10 neutrons

Each complete lithium atom has 3 electrons.III As shown in th e orbit-type d iagram, the

elec tron arrangement is:l . Sh ell No. 1: 2 e-2. Sh e ll No. 2: 1 e-

I The electron configurat ion of lithium is 2, l .

Every neon atom h as 10 electrons.III The electron arrangem ent is:

] . Sh ell No . 1: 2 e-2. Shell No. 2: 8 e-

BI The electron co nfiguration of neon is 2, 8.

On a separate sheet of paper, draw orbit-type diagrams of the electron ar rangement in atoms of elementsbetween lith ium and neon. Across Period 2 each successive e lectron goes into the second shell.)

Number [ f elefi:'tnons per heUIi1 The sh ells can be compared to sh elves in a bo okcase . The sh elves can be em p ty or th ey can have books

on them. The books cannot be be twe en sh elves . There is a ma x imum number of books which can fit oneach she lf. Similarly, electrons canno t be between shells and there is a m ax imum number of electronswh ich can fit in each shel L

Maximum number of electrons = nwhere 11 = th e shell number Shell No . 1 Shell No. 2 etc.)

El When the number of electrons in the third shell reaches 8 (argon at om s), elec trons start to fill thefourth she ll.

o The electron configuration of potassium at oms is 2 8, 8, l . There are places left for mo re electrons inthe third sh el l. These remain ing third shell vacancies are filled by electrons of transition metal a to ms.

a) Compile a table using the following head ings for elements in order from atomic no . 1 to no. 20.Element Atomic no. 1st shell e- 2nd shell e- 3rd shell e - 4th shell e-Hydrogen 1 1

b) After argon, how many places remain to be filled in the third she ll?A tomh radius

f l The nucleus is only about 1/10 000 of an atom s radius. The size of an atom is determined by th espace taken up by its electrons. The more electron sh ells the bigger the atom.

Ell The Period number indicates how many electron sh ells are occupied in atoms in that period , e.g.ato m s in Period 1 ha ve 1 shell occupied; atom s in Period 7 hav e 7 shells occupied.

ril Trend: Atomic radius increases down each Group of the Periodic Table.Refer to electron configuration to explain why:a) the smallest atom in Group VII is fluorine and th e largest is astatine;

b) silicon at oms have larger diameters than nit rogen atoms.

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11

11

rPeIl"Brm: lO([ T i l b ~ e p1iBltterlllllE tr: t f 0 m r fmHirug m mrtt mJ tn tr tlt [ l rra [C[] l1l1t]

L;l Trend: Atomic radius decreases from left to right across each Period of the Periodic TableThe negative elec trons are attracted by positive protons in th e nucleus. The greater the posi tive chargein the n uc leus, the stronger the force on the ou ter shell of electrons in ea ch row of the Periodic Table .

The table below contains data to sh ow the trend in atomic radius across the third Period.a) Complete the table.

Cb) Use graph paper to construct a graph illustrating the trend in atomic radi us .i) All th e atoms are in the sa me period . What does their atomic radius depend on?ii) Name the x-ax is of your graph.iii) Name the y-axis of your graph.

(iv) Extrapolate the graph to estimate the atomic radius of argon.AtomNaMgAlSipSClAr

Atomic num be r Z) Elec tron configuration Nuclea r charge Atomic radius nm)0.1 560.1360.1250.1170.1100.1040.099

The atomic radii of arsenic, selenium and bromine are 1.22 x 10 - 10 m, 1 16 X 10 - 10 m and 1.14 X 10 - 10 rn,respecti vely.a) Describe the trend in these measurements.

Cb) Relate the trend to the pOSition of these three elements in the Periodic Tab le.

c) Refer to atomic structure to exp lain the trend.

In ea ch of the following pairs of el ements, which atom has its ou te r electrons closest to its nucleus? Give a reasonfor your answer in each case.a) hydrogen and helium

Cb) neon and heliumCc) helium and lithiumCd) lithium and berylliume) lithium and sodium

In ea ch of the following pairs, from which atom would it be easier to remove an el ectron?Ca) hydrogen and lithiumCb) calcium and st rontium _ _ _Cc) oxygen and fluorineCd) ca lcium and ge rmanium

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IPtE [i'"6IlJldO[ l f i l l b J ~ f E PiBlitittE l"rrTI~ O - C ~ @ l t Bf

irJl ra" a 1:h::Ull lE fJ1 e f g ~

D

Sl In any atom, the moving electrons are held in the space around the nucleus by the attraction of thepositive nu cleus . Electrons can be removed from vaporised atoms by using an electron gun to knockelectrons out of complete atoms and change the atoms into positive ions . The voltage of the gun can beadjusted to remove one, two, three or more electrons from each atom.The first ionisation energy is the energy needed to remove one electron: X 7 X+ eThe second ionisation energy is the energy to remove a second electron : X+ 7 X++ e-

I II Other ionisation energies (3rd, 4th, 5th, etc.) are the energies needed to remove successive electrons.Units of ionisation en ergy : megajoules per mole of electrons (1 mole = 6.02 x 1 23 )

Successive ionisation energies (IE3 q JEs etc.) compare the difficulty of removing electrons, one by one,from an atom.Neon, atom ic no. 10, has the following successive ionisation energies :IE1 IE2 IE3 IE4 IEs IE6 IE7 IEs lEg IE102.09 4.00 6.13 9.38 12 .18 15 .25 20 .01 23 .08 115 .39 131.44 MJ mol-1Ca) How ma ny protons are there in the nucleus of a neon atom?Cb) After the first electron has been removed, how many electrons remain?Cc) How many protons in a Ne9 ion? How many electrons?(d) Explain why IE 10 is much larger than IE1 .e) How much energy is needed to form ions? MJ mol - 1

rends in ionisat ion energyThe following table lists first and second ionisation energies for elements atomic number (Z) 1 to 20 in thePeriodic Table .

Z Element IE1 IE2 Z Element IE1 IE21 H 1.32 11 Na 0.50 3.962 He 2.38 5.26 12 Mg 0.74 1.463 Li 0.53 7.31 13 Al 0.58 1.824 Be 0.91 1.76 14 Si 0.79 1.585 B 0.81 2.43 15 P 1.02 1.916 C 1.09 2.36 16 S 1.01 2.267 N 1.41 2.86 17 Cl 1.26 2.308 0 1.32 3.40 18 Ar 1.53 2.679 F 1.69 3.38 19 K 0.43 3.06

10 Ne 2.09 4.00 20 Ca 0.60 1.15

r I Trend: The first ionisation energy increases across each Period of the Periodic Table.11 (a) Refer to atomic radius to explain the trend in first ionisation energy across a Period.Cb) Write symbols for the ions created when (using an electron gun):

(i) 0.74 MJ mol- 1 is applied to magnesium atoms(ii) 3.45 MJ mol- 1 is applied to carbon atoms

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IJ

11IJ

[ p l ~ r B [ ] d G ( [ l f B l b J ~ r e pliBJttre r[f]~ ~ i l n l 1 i ] J1 t ~ NTI l J 1 H ~ rg @J 1 j ~ ] ~ tcItEl tr J fB1}f f in i ty [f 1Jnto]

Trend: Ionisation energy decreases down each Group of the Periodic Table.Ca From the table on the previous page, select elements which are all in one Group of the Periodic Table. List

them in order of increasing atomic number and complete the table below.Group eLments lectron co nfig uration of atom IEl M J moL l lectron configu ration of X ion

Cb) Use the electron configuration to explain the decrease in first ionisation energy down a Group.

Ca Graph IE l against atomic number for elements in the table on the previous page.Cb) Use electron configuration to expla in why IE l value falls after each Group VIII element.

Ca Write the electron configuration of Li - , Na and K ions. ___________________Cb) Which complete atoms have the same electron configurations? ________ _ _ ______Cc) Ci) Which elements listed on the previous page have peak IE2 values7

Cii) Explain why these elements have peak IE2 values. ___ ______________ ___

11 The following table lists the first ionisation energy of elements with consecutive atomic numbers.Element A B c o E F G0.95 1.15 1.36 0.41 0.56 0.61 0.67

Which element CA, B, C, D, E, F, G) is:Ca a Noble gas?Cb) a Group I metal? _ _____Cc) a halogen? ______

l t r on f f in i tyIII lectron ffinity is measured by the energy released when an electron is added to an atom, forming anegative ion. The greater the energy, the higher the electron affinity.III Atoms such as sodium and potassium have low electron affinity. Halogens have high electron affinity

and form negative ions (e.g. Cl - , Bc easily.B The general trend in electron affinity in the Periodic Table is similar to the trend in ionisation energy,

with the exception of the Noble gases (Group VIII) which ha ve low electron affinity.g Electron affinity increases across a Period and decreases down a Group.

IllI Electronegativity is a similar concept to electron affinity but electronegativi ty cannot be measured . Theterm electronegative is used when comparing atoms abilities to attract electrons, e.g. chlorine is muchmore electronegative than sodium.11 Ca Atoms of the element have the greatest electron affinity.

Cb) Atoms of the element have the lowest electron affinity.Cc) Sodium is slightly electronegative than potassium but much

electronegative than chlorine. m erald City Boo ks 1998. Th is sheet may be photocopied for non-commercial classroom use. 33


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PIE ro[]/dilC f i B l l b J ~ t e P l i a t t t ~ l r g - ] m [ t Er n m: lUJ TIllrBgj [l8 rr@ ttD(Q;) Em lrn Wv

rE ec:t.IrOIl1 lConfDgu ra th ]n

D

rIiI In orbit-type diagrams of atomic structure, electrons are shown in layers. When atoms join together,electrons in the outer layer interact. The ou ter shell is called th e valence shell. Elec trons in the outersh ell are th e valence electrons.

iii Electron configuration of Group VIII elements:1. He ..22. Ne...2,83. Ar...2, 8, 84. Kr...2 8, 18, 85. Xe...2, 8, 18, 18, 86. Rn ... 2, 8, 18, 32, 18, 8

I i1l Group VIII elements (Noble Gases):1. have the highest ionisa tion en ergy in each row of the Per iodic Ta bl e; it is very diffic ult to remove anele ctron from th e outer sh ell of th eir atoms;2 . are in ert (unreactive); their out er sh ell electrons do not interact with va lence electrons of other

at om s;3 . are monatomic gases composed of individual a tom s; their atoms do not jo in to gether to m ake

molecules.(a) Which Nob le Gases have com plete ou ter shells? _ _ _ _ _

(Formula: Maximum number of electrons = 2 where is the shell number.)(b) Select words from the word bank and fill in the spaces in the sentences below:

althoughlack

neonincomplete

arg oneight

kryptoncompounds

xenonfeature

eachcase

The Noble Gases do not form chemical -'; they are chemically inert. Their atoms do not evenjoin to _ _ other. Their _ of reactivity indicates that the outer shells of allNoble Gas atoms are complete but this is not the _ _ _ _ _ _ _ _ the outer shells ofhelium and contain the maximum number of e lectron s, those of _ _ _ _ _ --'

_ _ __ _ and radon are incomplete. All those with _ _ _ outershel ls have eight el ectrons in the outer shell. This common _ _ _ _ of these unreactive elementssuggests that _ is a stable number of electrons.

III Atoms combine to achieve a stable number of electrons in the outer shell.Stable number of electrons in the ou ter shell = 8.for small a toms with only one electron shell , stable number = 2.

i j Two ways in which atom s achieve a stable number of outer she ll elec trons are as follows:1. by transferring va lence electrons. 2. by sharing va lence elec trons with ot h er

Metals combin e with non-metals in atoms. Combinations of non-metals occurthis way. in th is way.

elect rontransferredouter ' - - - - - , , , - - - - - - It oute rshell , 'It" '" hellsodium t::::\ @ chlorineatom Cl tom

IIonic bond: strong attraction between positiveand negative ions

sha rede l e c t r o n ~ . . __ _ .

outer . ' . outershell , - - - - - shellhydrogen , f.:\ @l chlorineatom '- 0J /J) at om

Covalent bond: atoms held together by pair ofelectrons moving between them

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iPetrHlDltdlofC 1 r i B l b l ~ e lPliBJititetrIT1lr ( C Lt ff fQ (b &Q] [B if0 j@jEl @ 1tBtUrn @j lITHIDv lenC I ([ontc]

VaHeifU:Y

11

I 'l The valency of an element is the number of electrons which its atom needs to gain, lose or share withanother atom to ac h ieve a stable number in the ou ter shell . Noble Gases have stable numbers ofelectrons. The ir valen cy is O.Some examples are:1. Sodium (metal) has a val en cy of 1. After a sodium atom loses 1 electron to a non -metal atom it has

a stable sh ell of 8 electrons.2. Chlo rine (non-meta l) h as a va lency of 1. By ga in ing 1 electron fro m a metal or by sharing 1 electron

with another non-metal, a chlorine atom will have the stable number of 8 electrons in its outer shell.El rends in va l ency :

roupValency

I1

II2

Metals nd non meta ls combining

III3

(a) How many valence electrons are there in:(i) a magnesium atom?

IV4

V3

V2

V1

Vo

(ii) an oxygen atom?(b) When magn esium joins to oxygen , g ~ ions and 0 2 - io ns form.

(i) How many electrons were trans ferred ?(ii) Which atom lo st the electrons?(iii) Which at om gained the electrons?

(c) How many electrons are there in the outer shell of:(i) a Mg2+ ion? (i i) an 0 2- ion?

Non metals combining Molecules of the co mpound ammonia form when nitrogen and hydrogen atoms combineby sharing electrons. The valency of hydrogen is 1.(a) In which Group is nitrogen?(b) What is the va lency of nitrogen?(c) How many electrons does a ni t rogen atom need to make a stab le outer shell? _ (d) How many el ectron s does each hydrogen atom have ava ilable for sharing?(e) How many hydrogen atoms share electrons with one nitrogen atom?Diatom ic elements: hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine are composed ofmolecules in which ea ch molecule contains two atom s. The two at om s are joined by a covalent bond. DiagramA sh ows how tw o fluorine atoms combi ne by sha ring electrons . Diagram B shows how three fluo ri ne atom smight join .

A

sha red, - Q ~ - , : ~

{ ' ~\ I \ I\ , - -0-0 6 0

(a) Including the shared electrons, how manyelec trons does each fluorine atom have?

only outershellelectronsshown

shared shared(

pair pa i r_,-G-{1 / G'0 ,_ Gi-i/

C g ) \ / \0-0- ' -0 .0

(b) s this likely to happe n? Exp la in your answer.

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PlE lru[][lnlC l f i O l b ~ 2 pattelfH1lM t ill @J ]1 ITlB tr D J Cl f J m H ~ t@B g LI fhJ dJ Bt: CID0pr to.

I P l h l y 5 i i l I : : : C ~ pr llp rtirE iOlfnld ihorrndnng2 The higher the melting point of a solid element, the stronger th e forces between the particles which

make up the solid.I:J The higher the boiling pOint of an element in its liquid state, the stronger the forces between th e

particles of th e liquid.il The density of an element depends on the size of the particles and on how closely packed th ey are.a The ability of an element to conduct electricity is due to the presence of electrons which are free to

move.I ; A shiny lustre results if some of the electrons are easily excited by absorbing light energy. Visible lightis emitted when these electrons fall back to their lower ground state energy levels.l The melting point, boiling pOint, density (at 25 C and 101.3 kPa) and electrical conductivity (a t 25C)are li sted below for elements of atomic number 1 to 20.

Element MP (0C) P (0C)PeriodH - 259 - 253He - 272 - 269Period 2Li 180 1342Be 1278 2970B* 2300 3660C (graphite) >3550 Sublimes

(diamond) >3550 SublimesN - 210 - 1960 - 219 - 183F - 220 - 188Ne - 249 - 246Period 3Na 98 883Mg 650 1110Al 660 2450Si * 1410 3267P (white) 44 280

(red) 41 7 Sublime sS (\ allotrope) 113 445Cl - 101 - 35Ar - 189 1 86Period 4 (incomplete)K 63 760Ca 839 1484Note - indicates little or no conductivity .

* indicates a semi -metalCa) Graph MP agai nst atomic number for elements in Period 3.Cb) Describe the pattern of melting po ints across Period 3.

P g cm - 3 )

8.25 X 10 - 51.64 X 10- 4

0.531.852.342.253.511.15 X 10 - 31.31 X 10 - 31.55 X 10- 38.25 X 10- 40.971.742.702.331.822.352.072.90 X 10 - 31. 63 X 10 - 30.861.55

10 .52910 - 100.0710 - 17

21233810 - 710 - 17


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[ p l ~ [ j U ( O l t d l H ( [ i i B l b ~ { 2 Pii3Jititte Ifll1l~ ~ t ~ ~ ~ @Dl]OOJ [ T I H w D U D f f i ' I T l j ~ ' t t @ J i l l ~ ~ C 1 ] [ J u ~ ~ [ ; @ J Q

[[:ont jTrue or fa lse7a) All metals have higher densities than all non-metals.

Cb) All gases have much lower densit ies than all solids.Cc) Semi-meta ls have lowe r densities than metals . _

General characteristics of metals semi-metals and non-metalsMetalsGo od electrical conductorsK values 0.1 ILf l 1m 1Condu ctivity decreases withincreasing temperatureForm positive ions easily; do notform covalent bonds easi ly withother atoms

Semi-metals: B Si Ge As lPoor electrical co nductorsK values 10 - 3 - 10 - 10 f LD -1 m-1Conductivity increases with smallamounts of impuritiesForm covalent bonds with otheratoms

trrul ture o element

Non-metalsVery poor electrical conductorsK values


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P ~ I r H [ l J ] d J H [ [ l f i a l b ~ r e l P l i a l i t t ~ f I l l l

~ t t ~ ~ ~ U m [ r r n ( I D r r n C ' 3 m r n ~ i 1 : @ B ~ ~ a : f T I H ~ ~ O C @ j i l l

[ h e m h a ~ pnOperto Metal characteristics:1. form positive ions in chemical reaction2. usually produce hydrogen gas with dilute sulfuric acid3. oxides are basic - they react with acids

IfJ Non-metal characteristics:1. join to other atoms by covalent bonds to make molecules2. form negative ions in reaction with strong metals3. oxides are acidic - th ey react with basesSome chemical reactions of Period 3 elementslement plus ...

Sodium

Magnesium

Au minium

Silicon

Phosphorus

Sulfur

Chlorine

hydrogen gas and heatedVery fa st reaction formsNa and H- ionsVery fast reaction formsg z and H ions

No reaction

No reaction

No reaction

Slow reaction for msHzS moleculesFast reaction formsHCl molecules

oxygen gas and heatedVery fast reaction formsNa and Oz- ions;so dium oxide is basicVery fas t reaction formsg z and Oz- ions;

magnesium oxide is bas icFast reaction formsl3 and Oz- ions;

aluminium oxide isamp ho teric reacts withacids and with bases)Slow reaction forms SiOzcova lent networkcompound);s ilicon oxideis weak ly acidicFast reaction forms P4 01mole cules; phosphorusoxide is acidicSlow reactionforms SO z molecules;sulfur oxide is acidicNo reaction with oxygen ;chlorine ox ide is acidic

dilute sulfuric acid cold)Violen t reaction formsand S O ions and HzmoleculesVery fast reaction forms Na and S O ions and HzmoleculesFast reaction forms Al3 andSO ;,- ions and Hz molecules

No reaction

No reaction

No reaction

No reaction

Q Trend: Metallic character decreases from left to right across each Period of the Periodic Table.Choose one of the chemical characteristics of metals and use examples from the table above to illustrate the trendin metallic character.

l Trend: Metallic character increases down each Group.a) List the elements in roup V in order of increasing atomic number.b) Suggest the correct order for the fo llowing statements for each Group V element listed:

0 acid ic oxide[J amphoteric oxideEl bas ic oxidel acidic oxide

[J amphoteric oxide

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P E rD[JJdulC 1 f i B l ~ ~ t e [plDlitittE [i[ilJj[ f j f f ~ E t ~ ~ ~ @ B [ f ~ ~ ~ l U l ~ ~ r t f f i ~ i l l ~ ~

The electrons circled the nucleus in particular orbits. The electrons in each orbit had a p articular energy.Boh r s model was based on a study of absorption and em ission spec tra . The model worked well toexplain small atoms such as hydrogen . For atoms with many electrons, the emission and absorptionspectra had a lot more lines than could be explain ed by the Bohr model of the atom .

Quantum mechanical model o Schrfidinger and []ircu:Iiil This model was based on mathematical equations which gave the probability of finding an electron in

space around the nucleus. The multiple solutions to the equatiOns can be visualised by threedimensional drawings of orbital s. An orbital is th e shape of the space in which an electron is likely tobe found.

Iil Similarity of the Bohr model an d the quantum mechanical model: both have quantum numbers n = 1,2, 3 etc.) indicating energy levels of electrons around th e nucleus .

ml Difference: circular orbits described the movement of electrons in the Bohr model; orbitals describe th evolumes of space around the nucleus occupied by moving electrons in the quantum mechanical model.

O. bi1:alOrbitals are named 5, p d and fAxes e, y and z) are usuallyincluded in the drawings to indicate the three-dimensionalorientation of th e orbitals. The atom s nucleus is at theintersection of th e axes. (The letters stand for sharp ,princip al , d iff use and fundamental wh ich refer to

spectral lines .)I't 5 orbitals are spherical.11 An 5 orbital can hold a maximum of 2 electrons.Ill p orbitals are dumbbell-shaped.III p orbitals are in sets of 3.I l Px' Py and Pz can each hold up to 2 electrons. A set of p orbitals can hold a m ax imum of 6 electrons.Iil d orbitals are in sets of 5.11 Ea ch d orbital in the set can hold up to 2 electrons.IIiI A set of l orbitals can hold a maximum of

10 electrons.II t orbitals are in sets of 7; a set of t orbitals can hold a

maximum of 14 electrons.

Subhells

y_ xS

y y y

->: J r ~ .. .. x x xp, , p,y y yx . xd , . . dy y

... x x,. d,' . d

Subshells are different types of orbitals within the shell/principal quantum number.o Comp lete the following table:n123

4

Number of subshells1

Types of orbitals55P5Pd5Pdf

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aximum number of e in each subshell

39


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Fun elelL tlron configurat ion

11

g This shows the electrons of an atom in shells and orbitals. For example:Sodium atom electron configuratio

Si mple electron configuration : 2 8, 1Fu ll electron co nfiguration: 152 252 2p6 351

Full electron configuration of arg on : 152 252 2p6 352 3p6Full electron configuration of calcium: 152 252 2p6 35 2 3p6 45 2Refer to the ta ble in Exerci se 1

eaningFirst shell 5 orbita l has two eSecond shell 5 orbital has two eSecond shell p orbital has six eThird shell 5 orbital has one e-

(a) Is the p subshell of the third shell complete in both argon a nd calcium? YES/NO.(b) Is the third shell complete in both argon and ca lcium? YES/NO. Explain.

Rules or writ ing electron conf igurat ion

11

1. Sub sh ells a nd shells are filled in o rder of increasing energy of th e electrons:15


41/49

1111

RiOldl i[ ii j[[itDwDityR ~ l ~ o a { [ t ~ v ~ t y ~ F r n t d r T I l ~ l f 0 ~ 8 f ~

Eil Some elements exist as stable forms on ly; others h ave some stable and some radioactive isotopes . Theelements of atomic numbers 84 to 92 exist only as naturally occurring radioactive isotopes .'J Some elements do not occur naturally on earth at all but they can be prepared artificially. These are

elements at omic n umber 43, 61 and 93-109. Th ey are all radioactive .(a) Shade elements 84 to 92 on a copy of the Periodic Table. Key them as naturally occurring radioactive

elements. (Alternatively, list these elemen ts by name.)(b) Using a different key, shade elements 43 ,61 and 93 to 109 on the same copy of t he Peri odic Ta bl e . Key them

as artificial radioact ive elements.

11 Half-life of a radioactive isotope is a measure of the rate at which it decays.Half-life is defined as the time taken for half the nuclei in a sample to decay.Radioactive decay is exponential:1. after 1 half-life, 50 of the sample remains2. after 2 half-lives, 25 of the sample remains3 after 3 h alf-li ves , 12.5 of the sample remainsHalf-lives vary greatly from very short (e.g. 4.2 x 10 - 6 s for 2 ~ ~ P O to very long (e.g. 4 x 10 12 years forI% Re).

III A gUide to the amount of isotope remaining is th e number of counts recorded by a Geiger counter. Thenumber of counts observed has to be corrected by subtracting background radiation. (Backgroundradiation is the radiation in the atmosphere from other radioactive sources. Normally th e backgroundradiation count is low.)

The half-life of the artificially created radioisotope 1; is 8.04 days . What fraction of the original at oms of 1 3 11 illremain after:(a) 8 days 57 minutes 36 seconds? _ _(b) 24.12 days? _ _(a) Use the information below to calculate the number of counts due to the decay of the radioactive isotope,

1 ~ ; Re. Background radiation = 25 counts S- l.Time o of counts S- 1 Corrected numberMonday 8 am 2441 2416Monday 8 pm 1827Tuesday 8 am 1233Wednesday 8 am 629Wednesday 8 pm 478Thursday 8 am 327Friday 8 am 176

(b) Using graph paper, plot this information as a line graph . Put time on the x-ax is and the number of counts onthe y-axis.

(c) From the graph, estimate the number of counts re co rded at 8 pm on Tuesday.(d) From the graph, determine the time for 50 (on e half) of the sample to decay.e) (i) From the graph, the half-life l ~ ~ R e is _ _ _

(ii) From information given above, the half-life of 1 Re is _

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R B l d ~ [ ] i B l ( [ i t D W D 1 l : l : 1 J

l 'V&J tt aD The following results were obtained from a sample of ~ ~ P m Corrected count = Observed count - 20

11

Time Corrected Time Correctedh:min counts S - l h:min counts S - l9:00 560 9:079:01 500 9:08 2209:02 446 9:09 1969:03 400 9:10 1809:04 355 9:11 1609:05 315 9: 12 1409:06 280

Ca) Using a second sheet of graph paper, plot this info rmation as a line graph.Cb) Find the half-life of ~ ; Pm. _ Cc) Why was 20 counts S- l subtracted from the observed values?

Cd) Use the graph to fill in the missing count at 9:07 in the list above.Ce) What count would you expect to be produced by decay of this isotope sample at 9.18 7Cf) Wh at proportion of the original number of nuclei would rema in at 9:187The rad ioactive isotope of carbon, 1 , is produced naturally in the upper atmosphere. This radioactive carbon isincorporated, along with non-radioactive carbon, into the bodies of living things. When an organism dies, no new4C is added to its body. The amount of radioactive 4 C remain ing in the skeleton, hair, wood, etc. is compared

with the amount in an organism living today. The age of the material can be determined using the half-life of 14 Cwhich is 55 68 years.Ca) Complete the following table. 100

% originaL 4Cremaini ng100.00050.00025.00012.500

6.2503.125

me eLapsedsince death years

o

Cb) Complete the decay curve for 4C on the axes provided.Cc) I

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