1. Periodic table IA IIA post- transition metals IIIA IVA VA VIA VIIA
IIA
post-
transition
metals
IIIA
IVA VA
VIA
VIIA
transition metals
IIIB
IVB VB
VIB
VIIB
VIIIB IB
IIB

2. Bonding in Solids repulsive Coulomb interaction between ions e e
between electrons
attractive Coulomb interaction
between ions and electrons
kinetic energy of electrons

3. Molecular (van der Waals) bond
Crystals of “inert” gases of group 0: Ar, Kr, Xe, Rn e e m2 m1 R
Van-der Waals, London
or fluctuating dipole
interaction

4. Molecular (van der Waals) bond
atom1
atom2
electron charge distribution
-1/4

5. IONIC bond + Energy balance Crystals: NaCl, CsCl, CaCl2 Cl- cohesive
+ 7.9eV
cohesive
energy + Na Cl
Energy
balance

6. IONIC bond: Madelung constantR
Madelung constant

7. IONIC bond: Madelung constant
NaCl~ 1.75
CsCl~1.76
ZnS (cubic)~1.64

8. Covalent bond Crystals: C, Si, Ge, H
Covalent bond is formed by two electrons, one
from each atom, localised in the region
between the atoms (spins of electrons are
anti-parallel )
Example: Carbon 1S2 2S2 2p2 C C 2D 3D
Diamond: tetrahedron,
cohesive energy 7.3eV

9. Covalent bond Hydrogen Methane molecule molecule H4 C H3 H1 H2 1S
H atom H2
molecule
Energy C H1 H4 H3 H2

10. Covalent bond Atoms in group III, IV,V,&VI tend to form covalent bond
Filling factor
T. :0.34
F.C.C :0.74

11. Metallic bond Atoms in group IA-IIB let electrons to roam in
a crystal. Free electrons glue the crystal
Na+ e-
Attract
Repel
Additional binding due to interaction of partially filled d – electron shells
takes place in transitional metals: IIIB - VIIIB

12. The Hydrogen bond
Hydrogen bond is formed between the most electronegative
atoms: F,O and N. Bonding energy is ~ 0.1ev
Bonding in DNA molecule F- H+ C H N
sugar O
adenine
thymine

13. Bonding in Solids Melting point (K) Molecular crystals Metals Ionic
Covalent
3000
2000
1000
organic
W(3683)
Mo(2883)
Pt(2034)
Fe(1808)
Cu(1336)
Al(933)
Pb(600)
Na(371)
Hg(234)
LiF(1143)
KCl(1063)
C(<3500)
BN(3270)
SiO2(2001)
Si(1683)
Ge(1240)