Q.Why does nitrogen show catenation properties less than phosphorus?

Step 1: What determines catenation tendency.

Catenation (self-linking of like atoms via single covalent bonds) depends on the strength of the E–E single bond, which in turn depends on the balance between bond-forming orbital overlap and repulsion between the non-bonding (lone pair) electrons of the two linked atoms.

Step 2: The N–N bond is weak.

Nitrogen atoms are very small, so when two N atoms are joined by a single bond, their non-bonded lone pairs are forced close together, resulting in significant lone-pair–lone-pair repulsion. This repulsion substantially weakens the N–N single bond (bond enthalpy of N–N is much lower than expected), making catenated nitrogen chains/compounds ($N_2H_4$ excepted, but longer chains) unstable.

Step 3: The P–P bond is comparatively strong.

Phosphorus atoms are considerably larger. This greater size keeps the lone pairs on adjacent P atoms further apart, substantially reducing lone-pair–lone-pair repulsion. As a result, the P–P single bond is much stronger and more stable than the N–N single bond.

Step 4: Consequence. …

Link catenation ability directly to E–E single bond strength, then explain why the N–N bond is weakened by lone-pair repulsion (small …

• Do not confuse this question (catenation ability via single N–N/P–P bonds) with Q12 (multiple π bonding leading to N₂ vs P₄ as elemental forms) — they use related but distinct reasoning (single-bond lone-pair repulsion here, vs π-overlap there). …