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

Solution

Chemistry ma’am · 4 steps

Find E first: the weakest E–E single bond belongs to nitrogen, and nitrogen has only four valence orbitals.

1. Non-metals only. In group 15, only nitrogen and phosphorus are non-metals. Arsenic and antimony are metalloids, and bismuth is a metal. So E is either N or P.
2. Weakest E–E bond. The N–N single bond is weaker than the P–P single bond. Nitrogen atoms are very small, so the N–N bond is short, and the lone pairs on the two atoms repel each other strongly. So E is nitrogen.
3. Count valence orbitals. Nitrogen's valence shell (n = 2) has only four orbitals: one 2s and three 2p. It has no d orbitals, so it cannot expand its octet. It can form at most four bonds, as in NH₄⁺, where the fourth bond is a coordinate bond.
4. So. The maximum covalency of nitrogen is 4, which is option (c).

The idea to keep. A period 2 element has only one s and three p orbitals in its valence shell, so its covalency can never go above 4. Covalencies of 5 or 6 need d orbitals, which start in period 3.

Answer from the NTA final answer key. Solution by PrepWiser.