The maximum covalency of a non-metallic group 15 element ' E ' with weakest E-E bond is:

We need to find the maximum covalency of a non-metallic Group 15 element 'E' with the weakest E-E bond.

Non-metallic Group 15 elements are: N, P, As.

Among these, the weakest E-E single bond is the N-N bond (bond energy ≈ 160 kJ/mol). This is because nitrogen atoms are small, and the lone pairs on adjacent nitrogen atoms experience strong repulsion, weakening the single bond.

For comparison, P-P bond energy ≈ 200 kJ/mol.

Nitrogen has the electronic configuration $$1s^2 2s^2 2p^3$$.

Since nitrogen is in the 2nd period, it has no d-orbitals available for bonding and cannot expand its octet.

Maximum number of bonds nitrogen can form = 3 covalent bonds + 1 coordinate bond (using the lone pair) = 4.

Example: $$NH_4^+$$ where nitrogen forms 4 covalent bonds.

The answer is Option A: 4.