Question

The single X−X bond made by N is weaker than that of P because:
A). Of repulsion between nitrogen nucleus due to
B). of repulsion between non-bonded electrons due to smaller size of nitrogen atom
C). of higher bond enthalpy of nitrogen
D). all of the above

Answer 1

Hint: Consider how would be the bonding structure of single bonds between two N-N atoms, and what is the difference is we have two P atoms instead of two N atoms

Complete step by step solution: Nitrogen has the unique ability among its group to form p$\pi$-p$\pi$ multiple bonds with itself and with other elements (e.g., Carbon, Oxygen). Heavier elements of this group do not form pπ-pπ bonds as their atomic orbitals are so large and diffuse that they cannot have effective overlapping. Thus, nitrogen exists as a diatomic molecule with a triple bond (one s and two p) between the two atoms. Consequently, its bond enthalpy (941.4 kJ $mol^{-1}$) is very high. On the contrary, phosphorus, arsenic and antimony form single bonds as P–P, As–As and Sb–Sb while bismuth forms metallic bonds in the elemental form. However, the single N–N bond is weaker than the single P–P bond because of high interelectronic repulsion of the non-bonding electrons, owing to the small bond length.

So, the correct answer is option B) The single N−N bond made by N is weaker than that of P because: of repulsion between non-bonded electrons due to smaller size of nitrogen atom.

Additional information: $N_2$ is so stable that it is considered one of the best leaving groups in chemistry and certain mechanisms are derived around this property. It is what also causes Nitrogen compounds to be one of the main components of explosives.

Note: Only the single X−X bond made by N is weaker than that of P but $N_2$ i. e. N in elemental state is way more stable than others of the same group because of Nitrogen making triple bonds with itself.