The maximum covalency of a non-metallic group 15 element ' E ' with weakest $\mathrm{E}-\mathrm{E}$ bond is :

<p>Among the group 15 elements (N, P, As, Sb, Bi), the lightest two (N and P) are commonly considered nonmetals. Of these, <strong>nitrogen</strong> (N) is known to have the <strong>weakest single bond</strong> to itself (N–N). </p> <p>The <strong>N–N</strong> single‐bond enthalpy ($\approx 160$\,kJ/mol) is lower (weaker) than the <strong>P–P</strong> single‐bond enthalpy ($\approx 200$\,kJ/mol). </p> <p>Therefore, the “nonmetallic group 15 element with the weakest E–E bond” is <strong>nitrogen</strong>.</p> <hr /> <h3>Maximum Covalency of Nitrogen</h3> <p>Although nitrogen typically forms <strong>three</strong> covalent bonds in neutral compounds (e.g., $\mathrm{NH_3}$), it can expand to <strong>four</strong> bonds in certain cationic species such as ammonium $\mathrm{NH_4}^+$ or $\mathrm{NF_4}^+$. In such species, nitrogen has a formal positive charge but is still forming four covalent bonds.</p> <p>Hence, the <strong>maximum covalency</strong> of nitrogen is <strong>4</strong>.</p> <hr /> <p><strong>Answer: 4 (Option C).</strong></p>