chem115 general chemistry i

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• WileyPLUS: RESOURCES   Reading content      Chapter Opener      2.1 Elements and Atoms are Described by Dalton's Atomic Theory      2.2 Atoms are Composed of Subatomic Particles      2.3 The Periodic Table is used to Organize and Correlate Facts      2.4 Elements can be Metals, Nonmetals, or Metalloids      2.5 Formulas and Equations Describe Substances and their Reactions      2.6 Molecular Compounds Contain Neutral Particles Called Molecules      2.7 Ionic Compounds are Composed of Charged Particles called Ions      2.8 The Formulas of Many Ionic Compounds can be Predicted      2.9 Molecular and Ionic Compounds are Named following a System      Summary      Tools for Problem Solving      Questions, Problems, and Exercises      Glossary      

• Office Hours Videos      Chapter 2, Problem 76      Chapter 2, Problem 83      Chapter 2, Problem 99a      Chapter 2, Problem 99b      Chapter 2, Problem 99c      Chapter 2, Problem 104a      Chapter 2, Problem 104b      Chapter 2, Problem 104c      Chapter 2, Problem 104d      Chapter 2, Problem 104e      Chapter 2, Problem 120a      Chapter 2, Problem 120b      Chapter 2, Problem 120c      Chapter 2, Problem 120d      Chapter 2, Problem 120e      Chapter 2, Problem 120f      Chapter 2, Problem 120g      Chapter 2, Problem 129      Chapter 2, Problem 130      Chapter 2, Problem 132      Chapter 2, Problem 138      

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Ch 2. Elements, Compounds and

Chemical Reactions

Brady & Senese, 5th

Ed.

2.1. Elements and atoms are described by Dalton’s atomic theory 3

Chemical Laws

• The law of conservation of mass - in a chemical reaction, the mass of the reactants (starting materials) will equal the mass of resulting products Implication: reactions involve the re-organization of

materials.

• The law of definite proportions- the ratio of masses of each element is fixed for a given compound Implication: Each atom has a fixed specific mass, thus

in unique combinations, the mass ratio is specific

2.1. Elements and atoms are described by Dalton’s atomic theory 4

Learning Check:

Magnesium burns in oxygen to form magnesium oxide. If 16.88 g of Mg are consumed and 28.00 g of MgO are produced, what mass of oxygen was consumed?

Question:

Two compounds of copper and chlorine exist with one having twice as much chlorine per gram of copper as the other. This is evidence of which law?

a: Conservation of Mass b: Definite Proportions c: Multiple Proportions

2.1. Elements and atoms are described by Dalton’s atomic theory 6

• Matter consists of tiny particles called atoms• Atoms are indestructible. In chemical reactions, the

atoms rearrange but they do not themselves break apart

Dalton’s Atomic Theory

+

2.1. Elements and atoms are described by Dalton’s atomic theory 7

Dalton’s Atomic Theory (Cont.):

• In any sample of a pure element, all the atoms are identical in mass and other properties.

• The atoms of different elements differ in mass and other properties.

• In a given compound the constituent atoms are always present in the same fixed numerical ratio.

NaCl has a 1:1 atom ratio on the atomic level and larger

John Dalton

2.1. Elements and atoms are described by Dalton’s atomic theory 9

Learning Check:

In a sample of MgO, there are 16.89 g Mg and 11.11 g O. What mass of O would there be in a sample that contains 2.00 g of Mg?

2.1. Elements and atoms are described by Dalton’s atomic theory 10

Your Turn!

In a sample of an unknown compound, the mass ratio of Cl to C is 47.227g Cl to 4.00 g C. In another sample, there are 0.553 g of Cl. What mass of C would be in this sample?

A. 0.1532 g

B. 6.52 g

C. 0.153 g

D. 0.0468 g

E. None of these

Question:

9 grams of water contain 1 gram of hydrogen. How many grams of water contain 3 grams of hydrogen?

a: 1/3 gram b: 3 grams c: 9 grams d: 27 grams

2.1. Elements and atoms are described by Dalton’s atomic theory 12

The Law Of Multiple Proportions

When two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.

• cements the idea that atoms react as complete (whole) particles.

• chemical formulas indicate whole numbers of atoms- not fractions

2.1. Elements and atoms are described by Dalton’s atomic theory 13

Using The Law Of Multiple Proportions

sulfur sulfur

dioxide trioxide

Mass S 32.06 g 32.06 g

Mass O 32.00 g 48.00 g

Use these data to prove the law of multiple proportions

2.1. Elements and atoms are described by Dalton’s atomic theory 14

Your Turn!

Two substances are formed from A and B. AB and A2B3. If the mass ratio of A/B in AB is 3.49, what is the ratio of A/B in A2B3?

A. 0.431

B. 3.49

C. 0.286

D. 2.33

E. not enough information given

2.1. Elements and atoms are described by Dalton’s atomic theory 15

Proof Of Atoms

• Since the early 1980’s, the Scanning Tunneling Microscope (STM) has been used

• A surface can be scanned for topographical information

• The image for all matter shows spherical regions of matter-- atoms

Atomically resolved STM image of clean Au(100). This image is made with an Omicron Low Temperature STM and RHK Technology electronics by Erwin Rossen, Eindhoven University of Technology, 2006. Parameters: p<1e-11 mbar, T=77 K, I_setpoint=6 nA, V_bias=1 mV, Au(100) surface is Ar sputtered (1,5 kV, 2uA, 30 minutes) and annealed (500°C, 30 minutes).

RadioactivityRadioactivity• One of the pieces of evidence for the One of the pieces of evidence for the

fact that atoms are made of smaller fact that atoms are made of smaller particles came from the work of particles came from the work of

Marie CurieMarie Curie (1876-1934). (1876-1934). • She discovered She discovered radioactivityradioactivity, the , the

spontaneous disintegration of some spontaneous disintegration of some elements into smaller pieces.elements into smaller pieces.

2.2 Atoms are composed of subatomic particles 17

Cathode Ray Tube (CRT)

A gas filled glass tube that has electrical charge applied at both ends.

Such a tube glows with light and is the precursor of the modern-day television screen.

2.2 Atoms are composed of subatomic particles 18

Discovery Of The Electron By JJ Thomson

• In 1897, Thomson placed a magnet near CRT and noted deflection of the beam

• Repeated experiment with an electrical field and noted that the discharge was deflected by an electrical field toward the (+) plate

• Announced discovery of (-) particle, later named “electron” by Stoney

2.2 Atoms are composed of subatomic particles 19

Determining The Charge On An e-: Millikan

2.2 Atoms are composed of subatomic particles 21

Rutherford’s Alpha Scattering Experiment

Most alpha rays passed right through the Au

A few were deflected off at an angle

1 in 8000 bounced back towards the alpha ray source

2.2 Atoms are composed of subatomic particles 22

Rutherford’s Nuclear Model of the Atom

• Since most of the alpha particles were not deflected, most of the atom is empty space.

• Since some of the particles were deflected, they encountered small particles of the same charge.

• Since some particles were reflected, there must be a small dense area.

The modern view of the atom was The modern view of the atom was

developed by developed by Ernest Ernest RutherfordRutherford (1871-1937).(1871-1937).

02m11an1.mov

“It was about as credible as if you had fired a 15-inch artillery shell at a piece of paper and it came back and hit you”

Question:

2.2 Atoms are composed of subatomic particles 25

Discovery Of The Proton

• Discovered in 1918 in Ernest Rutherford’s lab• Detected using a Mass Spectrometer

2.2 Atoms are composed of subatomic particles 26

Discovery Of The Neutron

• Chadwick determined that the nuclei of light atoms could be caused to disintegrate by being bombarded by alpha particles.

• In collision of alpha particles with Be, a free neutron was created

• the presence of the neutron confirmed in 1932

2.2 Atoms are composed of subatomic particles 27

Subatomic Particles

Particle Symbol Mass (u) Location Charge

electron 5.48579903(10-4) orbital 1-

proton 1.007276470 nucleus 1+

neutron 1.008664904 nucleus 0

-01 eor e

Hor 11

11 p

010 nor n

2.2 Atoms are composed of subatomic particles 28

• Dalton’s atomic theory states that atoms of an element have a constant, characteristic atomic mass or atomic weight measured in amu (u)

• Atomic masses are based on a standard mass, that of an atom of C

• 1 atom of Carbon-12 = 12 u• Thus 1 u = 1/12 the mass of a Carbon-12 atom

Atomic Mass

2.2 Atoms are composed of subatomic particles 29

• Most elements in nature are uniform mixtures of two or more kinds of atoms with slightly different masses

• Atoms of the same element with different masses are called isotopes For example: there are 3 isotopes of hydrogen and 4

isotopes of iron

• Chemically, isotopes have virtually identical properties

Isotopes

2.2 Atoms are composed of subatomic particles 30

Atomic Notation

• An element is a substance whose atoms all contain the identical number of protons, called the atomic number (Z)

• Isotopes are distinguished by mass number (A): Atomic number, Z = number of protons Mass number, A = (number of protons) + (number of

neutrons) Note that for atoms, A is greater than Z: the symbol is

top-heavy

• For charge neutrality, the number of electrons and protons must be equal

SyAZ

2.2 Atoms are composed of subatomic particles 31

This information can be summarized: Number of protons = 92 ( = number of electrons) Number of neutrons = 143 Atomic number (Z) = 92 Mass number (A) = 92 + 143 = 235 Chemical symbol = U

Mass number, A (protons + neutrons) Chemical Symbol Atomic number, Z (number of protons)

235 U 92

Example: uranium-235

Question:

How many neutrons are there in an atom of sulfur-33?

a: 16

b: 17

c: 33

d: 49

Question:

How many electrons are there in an atom of uranium-238?

a: 92

b: 146

c: 238

d: 330

Question:

2.2 Atoms are composed of subatomic particles 35

Learning Check:

Fill in the blanks:

symbol neutrons protons electrons60Co

81Br

36 29 29

2.2 Atoms are composed of subatomic particles 36

Your Turn!

How many neutrons are there in 52Fe?

A. 52

B. 55

C. 26

D. none of these

What is the total value of:

3 quarters, two dimes and one nickel?

2.2 Atoms are composed of subatomic particles 38

Naturally occurring chlorine is a mixture of two isotopes. In every sample of this element, 75.77% of the atoms are chlorine-35 and 24.23% are chlorine-37. The measured mass of chlorine-35 is 34.9689 u and that of chlorine-37 is 36.9659 u. Calculate the average atomic mass of chlorine.

Learning Check: Atomic Mass

2.2 Atoms are composed of subatomic particles 39

Your Turn

There are 2 isotopes of element Z. The first is 56.5% in abundance and has a mass of 152.3 u. If the atomic mass is 155.5 u, what is the mass of the other isotope?

A. 156 u

B. 44.5 u

C. 157. u

D. not enough information given

E. none of these

Question:

Copper has two stable isotopes, copper-63 and copper-65. What is the abundance of copper-65?

a: 5.75% b: 27.5% c: 50% d: 72.5% e: 95.5%

Question:

Problem Solving

Calculate the average atomic mass of chromium of naturally occurring chromium based on the information given for its four isotopes:

4.31% 50Cr of mass 49.946 amu,

83.76% 52Cr of mass 51.941 amu,

9.55% 53Cr of mass 52.941 amu and

2.38% 54Cr of mass 53.939 amu.

Problem Solving

Naturally occurring Gallium consists of two isotopes. Calculate the percent abundances of Ga-69 and Ga-71 when the atomic mass is 69.72 amu and the isotopic masses are 68.926 and 70.925 amu respectively

2.3. The periodic table is used to organize and correlate facts 44

Periodic Table1A 2A 3A 4A 5A 6A 7A 8A

1 2

H He

3 4 5 6 7 8 9 10

Li Be B C N O F Ne

11 12 13 14 15 16 17 18

NaMg 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B

Al Si P S Cl Ar

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

87 88 89 104 105 106 107 108 109 110 111 112 114

Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Uuu Uub Uuq

58 59 60 61 62 63 64 65 66 67 68 69 70 71

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

90 91 92 93 94 95 96 97 98 99 100 101 102 103

Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

arranged in numbered rows – “periods”columns called “groups” or “families”

2.3. The periodic table is used to organize and correlate facts 45

• Summarizes chemical and physical properties of the elements

• Mendeleev first arranged atoms by increasing atomic mass. Noted repeating (periodic) properties

• Modern table is arranged by increasing atomic number (Moseley)

Periodic Table

2.3. The periodic table is used to organize and correlate facts 46

• A groups = representative elements or main group elements

I A = alkali metals II A = alkaline earth metals

VII A = halogens VIII = noble (also inert) gases

• B groups = transition elements• Inner transition elements = elements 58 – 71 and 90

– 10358 – 71 = lanthanide elements

90 – 103 = actinide elements

Some Important Classifications:

2.3. The periodic table is used to organize and correlate facts 47

The modern periodic table

2.4. Elements can be metals, non-metals, or metalloids 48

Metals, Nonmetals, And Metalloids

2.4. Elements can be metals, non-metals, or metalloids 49

Your turn!

Which of the following is correct?

A. Cu is a representative transition element

B. Na is an alkaline earth metal

C. Al is a semimetal in group IIIa

D. F is a representative halogen

E. None of these are correct

2.4. Elements can be metals, non-metals, or metalloids 50

• reflect light (have metallic luster)• Can be hammered or rolled into thin sheets (are

malleable) and can be drawn into wire (are ductile)• Are solids at room temperature (except Hg) • conduct electricity and heat

Properties Of Metals

2.4. Elements can be metals, non-metals, or metalloids 51

Nonmetals And Metalloids

• Nonmetals Lack the properties of metals Tend to pulverize when struck with a hammer Non-conductors of electricity and heat Many are gases, a few solids, and one liquid

(Br) React with metals to form (ionic) compounds

• Metalloids Have properties between metals and nonmetals

Question:

Which is a fourth-period alkaline earth metal?

a: K

b: Ca

c: Zr

d: C

e: Sn

Question:

Which are almost always found in nature in pure elemental form?

a: alkali metals b: inner transition metals c: noble gases d: halogens e: metalloids

Question:

Which is not a characteristic property of most metals?

a: malleability

b: good electrical conductivity

c: ductility

d: poor heat conductivity

e: luster

Question:

Which describes a physical property? a: colorless b: flammable c: toxic d: reactive e: corrosive

Question:

www.americanbonanza.com

Question:

Question:

Question:

www.luxfer.com

2.5. Formulas and equations describe substances and their reactions 60

• Are symbols used to describe other elements in a compound

• elements and compounds• Free elements are not combined with another

element in a compound. Examples: Fe (iron), Na (sodium), and K (potassium) Many non-metals occur in groups of 2 (as diatomic

molecules)- H, O, N, F, Cl, I, Br Some elements occur as molecules: P4, S, S8, P10, O3 , etc…

Chemical Formulas

2.5. Formulas and equations describe substances and their reactions 61

• Specify the composition of a substance

• Fe2O3 is composed of the elements iron and oxygen in a 2:3 ratio

• CO(NH2)2 expands to CON2H4, but parentheses often group atoms to show the compound’s structure

Chemical Formulas (Cont.)

MOLECULAR FORMULASMOLECULAR FORMULAS

• Formula for glycine is Formula for glycine is CC22HH55NONO22

• In one molecule there areIn one molecule there are

2 C atoms2 C atoms 5 H atoms5 H atoms 1 N atom1 N atom 2 O atoms2 O atoms

Question:

How many atoms of hydrogen are present in the formula

(NH4)2HPO4? a: 5 b: 6 c: 7 d: 9 e: none of these

2.5. Formulas and equations describe substances and their reactions 64

Hydrates

• Hydrates are crystals that contain water molecules, for example plaster: CaSO4 • 2H2O When all the water is removed (by heating), the solid

that remains is said to be anhydrous (without water)

CuSO4CuSO4 •5H2O

2.5. Formulas and equations describe substances and their reactions 65

Learning Check: Count The Atoms In A Chemical Formula

• Na2CO3

• (NH4)2SO4

• Mg3(PO4)2

• CuSO4•5H2O

• ___Na, ___ C, ___ O

• ___N, ___H, ___S, ____O• ___Mg, ___P, ____O• ___Cu, ___S, ___O, ___H

2.5. Formulas and equations describe substances and their reactions 66

• 2 HCl(aq) + CaCO3(s) CaCl2(aq) + H2O(l) +CO2(g)

HCl and CaCO3 are called reactants CaCl2, H2O,CO2 are called the products Reactants are separated from products with “”

that means “yields”• States matter: for solids use (s), liquids (l), gases (g),

and for substances dissolved in water (aqueous solutions) use (aq).

• We will learn later that the behavior of the reactants differs based on their states!

Chemical Equations

Problem Solving

How many atoms are represented in each of the following expressions:

a) 3N2O

b) 2(NH4)2CO3

c) BaSO3

d) CuSO4•2H2O

e) (NH4)3PO4

f) Sn(SCN)2

g) MgSO4•5H2O

2.5. Formulas and equations describe substances and their reactions 68

Balanced Equations

• The number of atoms of each type must remain the same on each side of the arrow

• subscripts must not change- they define the identity of the substances

• Coefficients- numbers in front of formulas-- indicate the number of molecules of each type

• Balancing achieved by adjusting coefficients 2 H2 + O2 →2 H2O

2.5. Formulas and equations describe substances and their reactions 69

Balanced EquationsNote that the number of each type of atom balances

and that the coefficient applies to the entire formula

Guidelines for Balancing Equations:1) Balance elements other than H and O first

2) Balance as a group any polyatomic ions that appears unchanged on both sides of the arrow

3) Balance separately those elements that appear somewhere by themselves

• As a general rule you should use the smallest whole-number coefficients when writing balanced chemical equations

Balancing Balancing EquationsEquations

__C__C33HH88(g) + __ O(g) + __ O22(g) (g) __CO__CO22(g) + __ H(g) + __ H22O(g)O(g)

__B__B44HH1010(g) + __ O(g) + __ O22(g) (g) _ B_ B22OO33(g) + __H(g) + __H22O(g)O(g)

04m04an1.mov

N2O5 N2O4 + O2

NH4NO2 N2 + H2O

KOH + H3PO4 K3PO4 + H2O

NH3 + CuO Cu + N2 + H2O

Balancing EquationsBalancing Equations

Question:

Which equation is balanced?

a: P4+ F2 PF5

b: H2 + S8 H2S

c: H2 + O2 H2O2

d: Li + O2 Li2O

2.6 Molecular compounds contain neutral particles called molecules 74

• Molecules are neutral particles made of 2 or more atoms.

• Many molecular compounds contain hydrogen: Group NoblePeriod IVA VA VIA VIIA Gas 2 CH4 NH3 H2O HF Ne 3 SiH4 PH3 H2S HCl Ar 4 GeH4 AsH3 H2Se HBr Kr 5 SbH3 H2Te HI Xe

Molecules Form When Nonmetallic Elements Combine

2.6 Molecular compounds contain neutral particles called molecules 75

Alkanes

• Alkanes are hydrocarbons (contain only C and H)

• Always have a ratio of atoms CnH2n+2

• Named using a prefix designating the number of C

• All have –ane suffix.

C

1

2

3

4

5

6

7

8

9

10

Prefix

Meth-

Eth-

Prop-

But-

Pent-

Hex-

Hept-

Oct-

Non-

Dec-

Suffix

+ane

Name

Methane

Ethane

Propane

• Organic chemistry is a major specialty that deals with compounds containing mostly carbon and hydrogen

• Hydrocarbons contain only hydrogen and carbon and are organic compounds

• Alkanes are the simplest hydrocarbons General formula is CnH2n+2

1 = meth-

2 = eth-

3 = prop-

4 = but-

5 = pent-

6 = hex-

2.6 Molecular compounds contain neutral particles called molecules 77

Learning Check: Name that alkane

Your turn!

Which of the following is heptane?

A. C6H12

B. C7H14

C. C6H14

D. C7H16

Your turn!

Which is the correct name for C4H10?

A. methane

B. ethane

C. propane

D. pentane

E. none of these

2.6 Molecular compounds contain neutral particles called molecules 80

Other Organic Compounds

Alkenes- hydrocarbons with fewer H than the alkanes. CnH2n. Use the same prefixes, but have the suffix -ene. C2H4 : ___________ C3H6: _____________

2.6 Molecular compounds contain neutral particles called molecules 81

Other Organic Compounds (Cont.)

Alcohols- Replace one H in an alkane with an -OH group

• Same prefixes, suffix becomes –anol CH3OH is ____________ C2H5OH is _______________

Your Turn!

What is the name of CH3CH2CH2CH2OH?

A. butanol

B. propanol

C. pentanol

D. tetranol

E. none of these

Your Turn!

What is a formula for heptene?A. C6 H12

B. C7H14

C. C6H14

D. C7H16

E. none of these

Question:

What is the formula for hexanol?

A. C6H14

B. C6H13OH

C. C6H12OH

D. C6(OH)14

www.brynmawr.edu

2.7 Ionic compounds are composed of charged particles called ions 85

Ionic Compounds

• Positively charged ions are called cations

• Negatively charged ions are called anions

• subscripts in the formula always specify the smallest whole-number ratio of the ions needed to make a neutral combination (formula unit)

Fe O O2-Fe3+3232

2.7 Ionic compounds are composed of charged particles called ions 86

What About Ions?

• Number of p+ = number of e- if neutral• Number of p+ < number of e- if negative• Number of p+ > number of e- if positive• The number of p+ never changes when ions form

How does Ca form Ca2+?

How is N3- formed?

2.7 Ionic compounds are composed of charged particles called ions 87

Learning Check:

Fill in the blanks:

Symbol neutrons protons electrons60Co3+

81Br-

36 29 27

Question:

How many electrons are there in P3-

a: 12 b: 15 c: 18 d: 28 e: 34

Question:

How many protons are in Rb+

a: 36 b: 37 c: 38 d: 85 e: none of these

METALSMETALS

Group A metals: Group A metals:

charge=group#charge=group#

NaNa++

MgMg2+2+

AlAl3+3+

Transition metals have variable chargesTransition metals have variable charges

Stock SystemStock System indicates charge indicates charge

Iron(III) means FeIron(III) means Fe3+3+

NONMETALSNONMETALS

Charge = 8-Group#Charge = 8-Group#

CC4-4- carbidecarbide

NN3-3- nitridenitride

OO2-2- oxideoxide

FF--fluoridefluoride

Charges on Common IonsCharges on Common Ions

+1

+2 +3

-4 -3 -2 -1

2.8 The formulas of many ionic compounds can be predicted 93

Ionic Compounds Are Neutral

• The positive charge must balance the negative charge

• We could use trial and error to find the least common charge

-

+

-

+

-

+

2.8 The formulas of many ionic compounds can be predicted 94

Determining The Formula Of An Ionic Compound

• Practically, we can often accomplish this by making the charge magnitude (not the charge) of one ion into the subscript for the other. (The “Criss-cross” rule)

• If you choose this approach, make sure that the subscripts are reduced to the lowest whole number.

Al3+ O2- Mg2+ O2-

NH4+ PO4

3-

Your Turn!

Which of the following is the correct formula for the formula unit composed of potassium and oxygen ions?

A. KO

B. KO2

C. K2O

D. none of these

Your Turn!

Which of the following is the correct formula for the formula unit composed of Fe3+ and sulfide ions?

A. FeS

B. Fe3S2

C. Fe2S3

D. none of these

2.8 The formulas of many ionic compounds can be predicted 97

Transition Metals

Chromium Cr2+, Cr3+ Zinc Zn2+

Manganese Mn2+, Mn3+ Silver Ag+

Iron Fe2+, Fe3+ Cadmium Cd2+

Cobalt Co2+, Co3+ Gold Au+, Au3+

Nickel Ni2+ Mercury Hg22+, Hg2+

Copper Cu+, Cu2+

Post-transition Metals

Tin Sn2+, Sn4+ Lead Pb2+, Pb4+

Bismuth Bi3+

Transition And Post-transition Metals Usually Have Multiple Charges

2.8 The formulas of many ionic compounds can be predicted 98

Some Polyatomic Ions (Ions With Two Or More Atoms):

NH4+ Ammonium ion CO3

2- carbonate ion

OH- hydroxide ion H3O+ hydronium ion

NO2- nitrite ion SO3

2- sulfite ion

NO3- nitrate ion SO4

2- sulfate ion

ClO2- chlorite ion CrO4

2- chromate ion

ClO3- chlorate ion Cr2O7

2- dichromate ion

PO43- phosphate ion

2.9 Molecular and ionic comounds are named following a system 99

• Cations: If the metal forms only one positive ion, the cation

name is the English name for the metal If the metal forms more than one positive ion, the

cation name is the English name followed, without a space, by the numerical value of the charge written as a Roman numeral in parentheses

• Anions: monatomic anions are named by adding the “–ide”

suffix to the stem name for the element polyatomic ions use the names in Table 2.5

The Stock System Of Naming Ionic Compounds

Question:

What is the chemical formula of the ionic compound formed by aluminum and nitrogen?

a: AlN

b: Al3N3

c: Al3N2

d: Al2N3

www.rpi.edu

Name the following compounds

• K2S

• NiSO4

• CoF3

• (NH4)3PO4

• MoBr3

• Pb(NO2)4

Problem Solving

Write the formula:

• Potassium chloride

• Calcium oxide

• Aluminum hydride

• Tin(II) bromide

• Copper(I) iodide

• Calcium chlorite

Question:

What is the formula of the ionic compound formed by ammonium ion and phosphate ion?

a: NH4P

b: NH4PO4

c: (NH4)3P

d: (NH4)3PO4

e: NH4(PO4)3

www.agrium.com

Question:

What is the formula of copper(II) sulfate?

a: CuS

b: Cu2S

c: Cu2SO4

d: CuSO4

w1tp.com

Question:

What is the name of NaC2H3O2 • 3H2O?

a: sodium carbonate hydrateb: sodium carbonate trihydratec: sodium acetate hydrated: sodium acetate trihydratee: sodium hydrogen carbonate trihydrate

Chemicalforums.com

In BINARY COUMPOUNDS: first element by English

name, the second by appending the suffix –ide to its stem. Greek letter for each indicates number

Chemical Name as Name asSymbol Stem First Element Second Element O ox- oxygen oxide S sulf- sulfur sulfide N nitr- nitrogen nitride P phosph- phosphorus phosphide F fluor- fluorine fluoride Cl chlor- chlorine chloride Br brom- bromine bromide I iod- iodine iodide

Then use prefix…

Greek prefixes indicate number of each atom in binary molecular compounds

Greek Prefixes mono- = 1 (often omitted) hexa- = 6 di- = 2 hepta- = 7 tri- = 3 octa- = 8 tetra- = 4 nona- = 9 penta- = 5 deca- = 10

Examples: PF5 = phosphorus pentafluoride HCl = hydrogen chloride N2O5 = dinitrogen tetraoxide

Note: many compounds have common names, like water for H2O.

Ban DiHydrogen Oxidehttp://www.gopetition.com

Dihydrogen monoxide (DHMO) is colorless, odorless, tasteless, and kills uncounted thousands of people every year. Most of these deaths are caused by accidental inhalation of DHMO, but the dangers of dihydrogen monoxide do not end there. Prolonged exposure to its solid form causes severe tissue damage.

Symptoms of DHMO ingestion can include excessive sweating and urination, and possibly a bloated feeling, nausea, vomiting and body electrolyte imbalance. For those who have become dependent, DHMO withdrawal means certain death.

Dihydrogen monoxide:

• is also known as hydroxl acid, and is the major component of acid rain• contributes to the "greenhouse effect.“• may cause severe burns.• contributes to the erosion of our natural landscape.• accelerates corrosion and rusting of many metals.• may cause electrical failures and decreased effectiveness of automobile brakes.• has been found in excised tumors of terminal cancer patients.

Name the following compounds

• ClO3

• NF3

• HI

• BBr3

• N2O5

Question:

What is the name of SF4 ?

a: sulfur fluoride b: monosulfur tetrafluoride c: monosulfur tetrafluorine d: sulfur tetrafluoride e: sulfur tetrafluorine

genchem.chem.wisc.edu

Question:

What is the formula of tetraphosphorus decaoxide?

a: PO10 b: P4O2

c: P4O10

d: 4PO10

e: 40 PO

2.9 Molecular and ionic comounds are named following a system 113

2.9 Molecular and ionic comounds are named following a system 114

Learning Check: Name The Following

• Na2O

• K2O

• NH4ClO3

• Mg(C2H3O2)2

• Cr2O3

• ZnBr2

115

Overview: Molecules vs. Formula Units

• electrically neutral, discrete particles called molecules

• Neutral groups of charged particles called formula units

Summary of PropertiesHardness and brittleness

Molecular compounds tend to be soft and easily crushed because the attractions between molecules are weak and molecules can slide past each other

Ionic compounds are hard and brittle because of the strong attractions and repulsions between ions

Electrostatic ForcesElectrostatic Forces

The oppositely charged ions in ionic compounds are The oppositely charged ions in ionic compounds are attracted to one another by attracted to one another by ELECTROSTATIC ELECTROSTATIC FORCESFORCES..

These forces are governed by These forces are governed by COULOMB’S LAWCOULOMB’S LAW..

Melting pointsTo melt the particles in the solid must have sufficient

kinetic energy to overcome the attractions between particles

Molecular compounds tend to have weak attractions between particles and so tend to have low melting points

Many molecular compounds are gases at room temperature

Ionic compound tend to have strong attractions so they have high melting points

Nearly all ionic compounds are solids at room temperature

Importance of Coulomb’s LawImportance of Coulomb’s Law

NaCl, NaNaCl, Na++ and Cl and Cl--,,m.p. 804 m.p. 804 ooCC

MgO, MgMgO, Mg2+2+ and O and O2-2-

m.p. 2800 m.p. 2800 ooCC

Electrical conductivity requires the movement of electrical charge

• Ionic compounds: Do not conduct electricity in the solid

state Do conduct electricity in the liquid

stateThe ions are free to move in the liquid

state

• Molecular compounds: Do not conduct electricity in the solid

or liquid state Molecules are comprised of uncharged

particles

Question: A clear, colorless solid is brittle and conducts electricity

when molten but not when solid. Is this solid a sample of an ionic or covalent compound?

a: ionic b: molecular c: it’s equally likely to be either ionic or molecular d: it’s impossible to tell without additional information

Question:

Question:

Question: CuSO4 • 5H2O

www.crystalgrowing.com

Question:

www.aecc.ru

Question:

cavemanchemistry.com

Question:

Question:

Question:

In general, are the melting points of molecular compounds higher or lower than those of ionic compounds?

a: higher b: lower