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Atomaire bindingen
- ionische binding- covalente binding- metallische binding
Ionic bonding 1
E
0E
1s
2s
2p
2 1Li :1 2s s
1s
2s
2p
2 2 5F :1 2 2s s p
between a Li atom and a F atom
Ionic bonding 2
E
0E
1s
2s
2p
2 0+Li :1 2s s
1s
2s2p
2 2 6-F :1 2 2s s p
gives Li+ F- molecule
IonizationPotential
(IP)
Electron Affinity (EA)
Energy cost: E = IP(Li) – EA(F)
Ionic bonding 3
( )U r E
Ionic binding curve:
electrontransfer
2
0
1
4
e
r
Coulombattraction
ions
( )repU r
Paulirepulsion
Binding curve has stable minimum !!
Ionic bonding 4
only works between very dissimilar atoms !!
Ionic bonding in solids
NaCl structure CsCl structure
Na+
Cl- Cl-
Cs+
common salts have ionic bonding
structure determined by relative size ions
Covalent bonding 1
Model system: one electron in two wells
wells far apart wells close
ES < EA
electron wants to pull wells close !!
( )V x
Covalent bonding 2
H2 molecule: two electrons in two wells
E1E 1E
SE
AE
H atom H atomH2 molecule
allowed by Pauli
Covalent bonding 3
He2 molecule? four electrons
E1E 1E
SE
AE
He atom He atomHe2 molecule
no electronic bonding in He2
no stable He2 molecule !!
because of Pauli exclusion principle
Hetero-atomic covalent bonding
E
1s
1s
2s
2p
H F molecule
SE
AE
S
+ -H F polar bond !!
H atom F atom
Poly-atomic covalent bonding 1
H2O molecule
22
1s
1s
covalent bonding gives directional bonds !!
Poly-atomic covalent bonding 2
CH4 molecule: tetraeder
1s
1s
1s
1s
C hybrid orbital
Covalent bonding in solids
C, Si, ... have covalent bonding
diamond structure
and compound semiconductors: GaAs, ...
Metallic bonding in solids 1
positive ions
metal: one electron in many wells
( )V x
x
( )S x
x
has a wave-like character (delocalized) ( )S x
'Fermiology'
Twee verschillende metalen met elkaar in contact contact-potentiaal
Volgende (laatste) hoor-college:
Quantum theorie van electrische geleidingIsolatoren vs. (half)geleiders, supergeleiders
Terugblik op de gehele stof
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