Answer the question on basis of passage given below:
Nitrogen differs from the rest of the members of its group due to its small size, high electronegativity, high ionisation enthalpy and non-availability of d-orbitals. Nitrogen has unique ability to form \(p\pi-p\pi\) multiple bonds with itself and with other elements having small size and high electronegativity (e.g., C, O). Heavier elements of this group do not form \(p\pi-p\pi\) bonds as their atomic orbitals are so large and diffused that they cannot have effective overlapping.
Maximum covalency of Nitrogen is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 4
Covalency is the number of covalent bonds an atom forms. Nitrogen has only four valence orbitals (one 2s and three 2p) and no d orbitals in its valence shell, so it can form at most four bonds. It reaches this maximum in \( \ce{NH4^{+}} \), where the lone pair of \( \ce{NH3} \) forms a fourth (coordinate) bond with \( \ce{H^{+}} \):
\( \ce{NH3} \) + \( \ce{H^{+}} \) → \( \ce{NH4^{+}} \) (four N–H bonds)
A fifth bond would need a d orbital, which nitrogen does not have, so \( \ce{NCl5} \) does not exist although \( \ce{PCl5} \) does. So the maximum covalency of nitrogen is 4.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Anomalous Properties of Nitrogen – “… Nitrogen is restricted to a maximum covalency of 4 since only four (one s and three p) orbitals are available for bonding. The heavier elements have vacant d orbitals in the outermost shell which can be used for bonding (covalency) and hence, expand their covalence as in PF6−.”