Language of ChemistryLanguage of Chemistryincludes chemical includes chemical symbolssymbols of elements, of elements,

chemical chemical formulasformulas,,&& chemical chemical equationsequations

All known All known elementselements ((ca.100) ca.100) are arranged in are arranged in Periodic TablePeriodic Table. .

Each element has its own Each element has its own name name && chemical symbolchemical symbol::

Sodium Sodium NaNa Sulfur S Sulfur S Potassium KPotassium K Phosphorus PPhosphorus PHydrogen HHydrogen H CopperCopper CuCuOxygen Oxygen OO GoldGold AuAuIronIron FeFe MercuryMercury HgHgTinTin SnSn LeadLead Pb

11ststcharacter character is CAPITALis CAPITAL

22ndnd (if any)(if any)is lowis low--keykey

Pb

CoCo is element cobalt, while is element cobalt, while

COCO is carbon monoxide, a compound. is carbon monoxide, a compound. Compounds are formed by combinations of Compounds are formed by combinations of

elements, written as a elements, written as a chemical formulachemical formula::

COCO22 HH22OO CHCH44 BNBN

Combining into compounds, Combining into compounds, atoms change their properties:atoms change their properties:

Carbon Carbon CC is a black stone, sulfur, is a black stone, sulfur, SS is a is a yellowyellow powder, but carbon disulfide, powder, but carbon disulfide, CSCS22 is is a toxic liquid.a toxic liquid.

Rearrangement of atoms resulting in a Rearrangement of atoms resulting in a new chemical compound is new chemical compound is

a a CHEMICAL REACTION:CHEMICAL REACTION:

HH22 + Cl+ Cl22 →→ 22HClHCl

→→++

STRUCTURESTRUCTUREOF ATOMOF ATOM

HumphryHumphry Davy, by 1808, found that Davy, by 1808, found that

ELECTRICAL CURRENT DECOMPOSES SOME SUBSTANCES TO ELEMENTS:ELECTRICAL CURRENT DECOMPOSES SOME SUBSTANCES TO ELEMENTS:

(+/(+/--))

CuClCuCl2(aq)2(aq) →→ CuCu(s(s) ) + Cl+ Cl2(g)2(g)

Michael FaradayMichael Faraday (1791(1791--1867) introduced the 1867) introduced the concept of concept of IONSIONS as as ELECTRICALLY CHARGED ELECTRICALLY CHARGED ATOMSATOMS that move to the battery poles, according to the Coulomb law:that move to the battery poles, according to the Coulomb law:

++

- Cathode:

Cu2++2e- → Cuo

Anode: +

2Cl- -2e- → Cl2CationsCations (+) (+) travel to, & travel to, & discharge at discharge at cathode cathode [[--]]

AnionsAnions ( ( -- ) ) travel to, & travel to, & discharge at discharge at anode anode [+][+]

+ -

Cl- Cu2+

Thus: Thus: Element Element ClCl can exist either as can exist either as

a a neutralneutral atomatom (in free chlorine,(in free chlorine, ClCl22),),

or as a or as a negativenegative chloride chloride ionion, , ClCl--,,i.e. although i.e. although ClCl atoms do not disappear in a chemical atoms do not disappear in a chemical transformation, they somehow change transformation, they somehow change –– in their charge.in their charge.

Element Cu can exist as a Element Cu can exist as a neutral atomneutral atom, ,

or as a positive or as a positive copper ion, Cucopper ion, Cu2+2+∴∴atoms can either be neutral, or be electrically charged. atoms can either be neutral, or be electrically charged. ∴∴atoms, though never destroyed in chemistry, must have some atoms, though never destroyed in chemistry, must have some inner inner

structurestructure, with its , with its subatomic particlessubatomic particles..Jacob J. Jacob J. BerzeliusBerzelius put forwardput forward

The ELECTRIC THEORY OF CHEMICAL BONDThe ELECTRIC THEORY OF CHEMICAL BOND: : atoms are held together in compounds due to their opposite electatoms are held together in compounds due to their opposite electrical rical

charges: charges:

NaNa++ ClCl--

Only Only outer electronsouter electrons are involved in chemical are involved in chemical rxnsrxns

ELEMENTS IN PERIODIC TABLEELEMENTS IN PERIODIC TABLE

Each element as posted in the Table, has: Each element as posted in the Table, has: a a NAMENAME, potassium, hydrogen, , potassium, hydrogen, ……a a SYMBOLSYMBOL, K, Na, Cu, , K, Na, Cu, ClCl, , ……an an ATOMIC NUMBER ATOMIC NUMBER ZZ (integer only) & (integer only) & an an atomic mass atomic mass AA (usually non(usually non--integer)integer)

55.847

26 Fe

Atomic number Z is the positive charge of Atomic number Z is the positive charge of the nucleus & the number of protons in itthe nucleus & the number of protons in it

Atomic mass is the sum of masses of Atomic mass is the sum of masses of protons & neutrons.protons & neutrons.

Why is atomic mass non-integer?Because natural elements consist of a

mix of isotopes:Atoms with the same atomic number,

but different mass number.

Neon, Neon, NeNe: : Z=10Z=10 three isotopesthree isotopesp p nn AA

NeNe--2020 90.51% 10 90.51% 10 1010 2020NeNe--2121 0.21% 10 11 210.21% 10 11 21NeNe--2222 9.22% 10 12 229.22% 10 12 22The average Atomic mass is 20.18The average Atomic mass is 20.18

Copper, Cu: Copper, Cu: Z = 29 Z = 29 two isotopestwo isotopesCuCu--6363 69.17%69.17%CuCu--6565 30.83%30.83%At. mass = At. mass = 63 x 0.6917 + 65 x 0.3083 =63 x 0.6917 + 65 x 0.3083 =

= 63.55 = 63.55 a.m.ua.m.u..

ELEMENTS & PERIODIC TABLEELEMENTS & PERIODIC TABLE

To each isotope, besides a symbol, To each isotope, besides a symbol, two numberstwo numbers are are associated:associated:atomic number (atomic number (ZZ) ) -- position in the Table (element ID#)position in the Table (element ID#)mass number (mass number (AA))

2727means cobalt (Z=27) atom with its mass number A=59

5959Mass Mass

numbernumberSymbol

Atomic Atomic numbernumber

SUBATOMIC PARTICLESSUBATOMIC PARTICLESAlthough atoms are not destroyed, or disappear in Although atoms are not destroyed, or disappear in chemical chemical rxnsrxns, they have their inner structure: atom , they have their inner structure: atom consist of 3 types of consist of 3 types of subatomic particlessubatomic particles, with their , with their known electrical charges known electrical charges && masses. masses.

massmass chargechargePROTON PROTON pp+ 1+ 1 +1+1NEUTRON NEUTRON n n 11 00ELECTRON ELECTRON ee-- 00 --11

(1/2000)(1/2000)Masses are in ATOMIC MASS UNITS (Masses are in ATOMIC MASS UNITS (amuamu))

Protons Protons && neutrons are neutrons are heavyheavy particlesparticlesconstituting atomic nucleus. constituting atomic nucleus. The The massmass of atom is due to of atom is due to nucleusnucleuswhich is very small in size which is very small in size && positively positively charged.charged.That That charge is the atomic numbercharge is the atomic number..

ATOMIC NUMBER ATOMIC NUMBER Z Z is the NUMBER is the NUMBER of PROTONS in the NUCLEUSof PROTONS in the NUCLEUS

MASS NUMBER A is the SUM MASS NUMBER A is the SUM of PROTONS & NEUTRONS, i.e. of PROTONS & NEUTRONS, i.e.

A = A = ZZ + + nn

Electrons are almost weightless & spread around the nucleus.Electrons are almost weightless & spread around the nucleus.The The sizesize of atom is the size of its electron cloud.of atom is the size of its electron cloud.

Outer (valence)electrons

Atomic nucleus: protons & neutrons

Positive charge = number of protons,

mass = sum of protons & neutrons

Inner shell (core) electrons

Electron cloud:No mass, negative charge

Chemical propertiesChemical properties(i.e. ability to undergo chemical (i.e. ability to undergo chemical rxnsrxns) )

depend on thedepend on the electron configurationelectron configuration(primarily on the # of (primarily on the # of ee--), ),

which itself is equal to the number ofwhich itself is equal to the number of pp++ in a in a neutral atom neutral atom

(but not related to the number of neutrons)(but not related to the number of neutrons)∴∴ atoms with the same number of atoms with the same number of pp++

(i.e. same (i.e. same Z,Z, ∴∴ also the same number of also the same number of ee--) ) but different number of but different number of nn are are chemicallychemically indistinguishableindistinguishable, ,

even though their masses differ.even though their masses differ.

Atoms with the Atoms with the same same ZZ(number of protons or nuclear charge) (number of protons or nuclear charge)

but different number of neutronsbut different number of neutrons((∴∴ different masses) aredifferent masses) are ISOTOPES

Neon, Neon, NeNe: 3 isotopes:: 3 isotopes:ZZ A A nn

2020NeNe 90.51% 1090.51% 10 20 20 1010

2121NeNe 0.21% 100.21% 10 21211111

2222NeNe 9.22%9.22% 1010 22 1222 12The average atomic mass The average atomic mass A=A= 20.1820.18

10

Ne20.18

Copper, Cu: 2 isotopesCopper, Cu: 2 isotopes

Z A nZ A n6363CuCu 69.17%69.17% 29 63 29 63

34346565CuCu 30.83% 29 65 3630.83% 29 65 36

AA = 63= 63××0.6917 + 650.6917 + 65××0.3083 = 63.55 0.3083 = 63.55 amuamu

29

Cu63.55

Isotopes belong to the Isotopes belong to the same elementsame element, , have the have the same symbolsame symbol, occupy the , occupy the same same cellcell in the Periodic Table, in the Periodic Table, && have the have the same chemical properties. same chemical properties. ““ISOTOPEISOTOPE”” translates as translates as ““same placesame place””, , i.e. the same cell in Periodic Table.i.e. the same cell in Periodic Table.Mass number of each isotope is an Mass number of each isotope is an integerinteger number (number of protons)number (number of protons)Natural elements are Natural elements are mixtures of mixtures of isotopesisotopes..Atomic massesAtomic masses in the Table are not in the Table are not integerinteger: they are : they are averageaverage out of all the out of all the natural isotopes of any particular natural isotopes of any particular elementelement

Periodic TablePeriodic TableDmitryDmitry MendeleevMendeleev, 1869 arranged all known , 1869 arranged all known (60 by his time) elements according to their (60 by his time) elements according to their increasing atomic masses & noticed some pattern: increasing atomic masses & noticed some pattern: Properties of elements repeat each other with a Properties of elements repeat each other with a period of 7 elementsperiod of 7 elements (8 after the discovery of noble (8 after the discovery of noble gases, gases, && 18 for heavier elements) 18 for heavier elements) He organized the list of elements as a chart, so that He organized the list of elements as a chart, so that elements with similar properties stand under each elements with similar properties stand under each otherother in columns in columns –– groups.groups.He successfully He successfully predictedpredicted several several elements not yet elements not yet knownknown, , && predicted, very precisely, their properties: predicted, very precisely, their properties: they were later discovered in the nature, just where they were later discovered in the nature, just where MendeleevMendeleev advised to look for them.advised to look for them.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18IIAA VIIIVIIIAA

IIA IIA IIIIIIAA IVIVAA VVAA VIVIAA VIIVIIAA

PERIODIC TABLE PERIODIC TABLE OF ELEMENTSOF ELEMENTS

IIIB IVB VB VIB VIIB VIIIB IB IIBIIIB IVB VB VIB VIIB VIIIB IB IIB

Horizontal rows are 7 Horizontal rows are 7 PERIODSPERIODS..Vertical columns are 18 Vertical columns are 18 GROUPSGROUPS..Tall columns: Tall columns:

8 8 MAIN GROUPSMAIN GROUPS (I(IAA to VIIIto VIIIAA). ). Their elements are Their elements are REPRESENTATIVEREPRESENTATIVEELEMENTS. ELEMENTS. Short columns: Short columns: TRANSITION METALSTRANSITION METALS(Numbered as 3 to 12 or IB to VIIIB)(Numbered as 3 to 12 or IB to VIIIB)Two cells contain LANTHANIDE Two cells contain LANTHANIDE & & ACTINIDE families (which are both ACTINIDE families (which are both INNERINNER--SHELL TRANSITION METALS).SHELL TRANSITION METALS).

METALS METALS vs.vs. NONMETALSNONMETALSMost of elements are Most of elements are metalsmetals: :

they they conduct electricity, heatconduct electricity, heat, are , are malleable, easily malleable, easily release their electronsrelease their electronsproducing producing negative ionsnegative ions while forming while forming compounds with noncompounds with non--metalsmetals. .

Example: Example: Metal Zn combines with nonMetal Zn combines with non--metal sulfur S:metal sulfur S:

Zn Zn --2e2e-- →→ ZnZn2+2+

S + 2eS + 2e-- →→ SS22--

Almost all metals are solid (except mercury, Hg).Almost all metals are solid (except mercury, Hg).

NonmetalsNonmetals are in the are in the upper right cornerupper right corner of of the table. They exist as gases, liquids (as the table. They exist as gases, liquids (as bromine, Brbromine, Br22) or solids (carbon, iodine, ) or solids (carbon, iodine, phosphorus, sulfur, etc.) They do not phosphorus, sulfur, etc.) They do not conduct electricity.conduct electricity.

They more likely They more likely accept electronsaccept electrons from from metals, but also form compounds with metals, but also form compounds with other nonother non--metals:metals:

S + 2eS + 2e-- →→ SS22--

Zn Zn --2e2e-- →→ ZnZn2+2+

Net reaction is: Zn + S Net reaction is: Zn + S →→ ZnSZnS

S + OS + O22 →→ SOSO22

Between metals Between metals && nonmetals are nonmetals are semimetals or semimetals or metalloidsmetalloids..They are brittle solids They are brittle solids &&

semiconductors semiconductors (such as (such as SiSi, , GeGe).).

Diatomic gases:Diatomic gases:HH22, O, O22, N, N22, F, F22, Cl, Cl22

&& two other two other diatomicsdiatomics: : BrBr22((ll), I), I22((ss).).

Two liquid elements: Two liquid elements: HgHg & & BrBr22

In Periodic Table: In Periodic Table: Each Each groupgroup contains elements with similar properties.contains elements with similar properties.Within a group, metallic properties increase from top to bottom,Within a group, metallic properties increase from top to bottom,while nonwhile non--metallic properties decrease.metallic properties decrease.Some groups have their special names:Some groups have their special names:1st group (left column, IA), besides hydrogen, consists of1st group (left column, IA), besides hydrogen, consists ofalkaline metalsalkaline metals –– most active metalsmost active metals

In chemical In chemical rxnsrxns, they always lose 1 electron:, they always lose 1 electron:Na Na →→ NaNa+ + + + ee--

neutral atom positively charged ion (neutral atom positively charged ion (cationcation))2nd group (IIA) is 2nd group (IIA) is alkaline earth metalsalkaline earth metals

always lose 2 electrons:always lose 2 electrons:Ca Ca →→ CaCa+ + + 2+ 2ee--

Groups 3 to 12 are allGroups 3 to 12 are all transition metalstransition metals16th group (VIA) is16th group (VIA) is chalcogenschalcogens..17th group is 17th group is halogens (VIIA)halogens (VIIA) -- most active nonmost active non--metalsmetals

readily accept electron:readily accept electron:ClCl + + ee-- →→ ClCl--

neutral atom negative ion (anion)neutral atom negative ion (anion)18th group (right column, VIIIA) is18th group (right column, VIIIA) is noble gasesnoble gases –– nonnon--reactive reactive elements. elements.