The properties of elements are the periodic functions of their atomic numbers

Non-metallic elements are lesser in number than metallic elements

The first ionisation energies of elements along a period do not vary in a regular manner with increase in atomic number

For transition elements the d-subshells are filled with electrons monotonically with increase in atomic number.

2

4

3

1

CN^-

$$O_2^-$$

NO⁺

CN⁺

low bond energy

absence of bond polarity

unsymmetrical electron distribution

presence of more number of electrons in bonding orbitals