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1Chapter 2: Atomic bonding and properties
Atomic models
2Chapter 2: Atomic bonding and properties
Quantum numbers
•
p orbital
m1 = -1,0,+1
•
••
•
•
••
1/2
-1/2
s orbital
m1 = 0
m2 = -2,-1,0,+1,+2
d orbital
2
3Chapter 2: Atomic bonding and properties
p
d
f
s
4Chapter 2: Atomic bonding and properties
1s 2s 2pC
••••
•
•
↑
↓
2p
N
•
↑
↑
••••
•
•• ↓
O
↑
↓
•
↑
••••
•
•• ↓
• F
↑
↑
↓
•
↑
••••
•
•• ↓
•
•
Ne• inert gas• filled shell
↓
↓
↑
↑
↓
•
↑
••••
•••
•
••
+ 12 •↑
H+
••
↑
↓
+ 12
! 12
He
•••↑
Li
•••↑
↓•
Mg B
••••
↑•
3
5Chapter 2: Atomic bonding and properties
O
Se
Te
Po At
I
Br
He
Ne
Ar
Kr
Xe
Rn
F
ClS
Li Be
H
Na Mg
BaCs
RaFr
CaK Sc
SrRb Y
The Periodic Table• Columns: Similar Valence Structure
give
up
1egi
ve u
p 2e
give
up
3e iner
t gas
esac
cept
1e
acce
pt 2
e
6Chapter 2: Atomic bonding and properties
Electronegativity
Larger electronegativitySmaller electronegativity
4
7Chapter 2: Atomic bonding and properties
Force and energy vs. separation distance
8Chapter 2: Atomic bonding and properties
• Predominant bonding in ceramics
Ionic bonding
Give up electrons Acquire electrons
NaClMgOCaF2CsCl
5
9Chapter 2: Atomic bonding and properties
Covalent bonds
••
••• •
••C
H
HH
H
sharedelectronfrom H
sharedelectronfrom C
Sharing of electrons fromone atom to another
10Chapter 2: Atomic bonding and properties
Metallic bonds 'Cloud' of electrons
electron cloudaround + cores
Secondary bonds• Permanent dipoles-molecule induced
-general case:
-ex: liquid HCl
-ex: polymer
H Cl H Clsecondary bonding
secondary bonding
secondary bondingsecondary bonding
6
11Chapter 2: Atomic bonding and properties
Contribution of bond types
Metals
covalent
ionic
secondary
Polymers
Semiconductors
metallic
Ceramics and glasses
12Chapter 2: Atomic bonding and properties
• Bond length, r
• Bond energy, Eo
• Melting Temperature, Tm
Properties from bonding: Tm
r o r
Energyr
larger Tm
smaller Tm
Eo = “bond energy”
Energy
r o runstretched length
7
13Chapter 2: Atomic bonding and properties
• Coefficient of thermal expansion, α
Properties from bonding: α
ΔL
length, Lo
unheated, T1
heated, T2
r or
larger α
smaller α
Energyunstretched length
EoEo
