Nucleus: Z = # protons

orbital electrons: n = principal quantum number

n=3 2 1

= 1 for hydrogen to 94 for plutoniumN = # neutrons

Atomic mass A ≈ Z + N

BOHR ATOM

CHAPTER 2:ATOMIC STRUCTURE AND INTERATOMIC BONDING

WAVE-MECHANICAL ATOM

• have discrete energy states• tend to occupy lowest available energy state.

Incr

easin

g en

ergy

n=1n=2

n=3

n=4

1s2s

3s2p3p

4s4p 3d

Electrons...ELECTRON ENERGY STATES

Electron Configuration

• Columns: Similar Valence Structure

Electropositive elements:Readily give up electronsto become + ions.

Electronegative elements:Readily acquire electronsto become - ions.

He Ne Ar Kr Xe Rn

iner

t gas

es

acce

pt 1

e ac

cept

2e

give

up 1

e gi

ve u

p 2e

give

up 3

e

F Li Be

Metal

Nonmetal

Intermediate H

Na Cl Br I

At

O S Mg

Ca Sr Ba Ra

K Rb Cs Fr

Sc Y

Se Te Po

THE PERIODIC TABLE

Na (metal) unstable

Cl (nonmetal) unstable

electron

+ - Coulombic Attraction

Na (cation) stable

Cl (anion) stable

• Example: NaCl

IONIC BONDING

• Predominant bonding in Ceramics

Give up electrons Acquire electrons

He -

Ne -

Ar -

Kr -

Xe -

Rn -

F 4.0Cl 3.0Br 2.8

I 2.5At 2.2

Li 1.0Na 0.9K

0.8Rb 0.8Cs 0.7Fr 0.7

H 2.1

Be 1.5Mg 1.2Ca 1.0Sr 1.0Ba 0.9Ra 0.9

Ti 1.5

Cr 1.6

Fe 1.8

Ni 1.8

Zn 1.8

As 2.0

CsCl

MgOCaF2

NaCl

O 3.5

EXAMPLES: IONIC BONDING

• Example: CH4

C: has 4 valence e, needs 4 moreH: has 1 valence e, needs 1 moreElectronegativities are comparable.

COVALENT BONDING

shared electrons from carbon atom

shared electrons from hydrogen atoms

H

H

H

H

C

CH4

• Molecules with nonmetals• Molecules with metals and nonmetals• Elemental solids (RHS of Periodic Table)• Compound solids (about column IVA)

He -

Ne -

Ar -

Kr -

Xe -

Rn -

F 4.0Cl 3.0Br 2.8

I 2.5At 2.2

Li 1.0Na 0.9K

0.8Rb 0.8Cs 0.7Fr 0.7

H 2.1

Be 1.5Mg 1.2Ca 1.0Sr 1.0Ba 0.9Ra 0.9

Ti 1.5

Cr 1.6

Fe 1.8

Ni 1.8

Zn 1.8

As 2.0

SiCC(diamond)

H2O

C 2.5

H2

Cl2

F2

Si 1.8

Ga 1.6

GaAs

Ge 1.8

O 2.0

colu

mn

IVA

Sn 1.8Pb 1.8

EXAMPLES: COVALENT BONDING

• Primary bond for metals and their alloys

+ + +

+ + +

+ + +

METALLIC BONDING

• Fluctuating dipoles

HH HHH2 H2

secondary bonding

ex: liquid H2asymmetric electron clouds

+ - + -secondary bonding

SECONDARY BONDING

Ceramics (Covalent & Ionic bonding):

Metals(Metallic bonding):

Polymers(Covalent & Secondary):

secondary bonding

Large bond energylarge Tmlarge Esmall

Variable bond energymoderate Tmmoderate Emoderate

Directional PropertiesSecondary bonding dominates

small Tsmall Elarge

SUMMARY: PRIMARY BONDS