1. According to molecular orbital theory the atomic orbitals of large number of atoms in a crystal overlap to form numerous bonding and anti-bonding molecular orbitals without any band gap.

2. The bonding molecular orbitals are completely filled with an electron pair in each and the anti-bonding molecular orbitals are empty.

3. Absence of band gap accounts for high electrical conductivity of metals.

4. High thermal conductivity is due to thermal excitation of many electrons from the valence band to the conduction band.

5. With an increase in temperature, the electrical conductivity decreases due to vigorous thermal motion of lattice ions that disrupts the uniform lattice structure. that is required for free motion of electrons within the crystal.

Common Errors

1. The number of bonds formed by elements may go wrong.
2. When writing Lewis structure, electrons may be written in an irregular way.
3. Coordinate covalent bond should not be written as a line

Rectifications

1. Always hydrogen and fluorine form 1 bond Oxygen 2 bonds, Nitrogen 3 bonds, Carbon 4 bonds
2. When writing lewis structure, each atom should be surrounded by eight electrons in such a way as 4 pairs of electrons.
3. Coordinate covalent bond should be written from donor atom to acceptor atom as an arrow mark Donor→ Acceptor