Question

Explain the following observation:

Unlike phosphorus, nitrogen shows little tendency for catenation.

Answer 1

1. Nitrogen has a small atomic size and high electronegativity, favouring strong N ≡ N triple bonds rather than N-N single bonds needed for catenation.
2. The N-N bond has lower bond dissociation energy (163.8 kJ/mol) compared to the P-P bond (201.6 kJ/mol), making N-N bonds less stable.
3. Phosphorus atoms, being larger with lower electronegativity, form more stable P-P single bonds that favour catenation and form tetrahedral P₄ molecules.
4. Thus, nitrogen shows little tendency for catenation due to weaker N-N single bonds and preference for multiple bonding, while phosphorus forms stable P-P single bonds that support catenation.