Group 15 non-metals: N, P, As, Sb. The weakest \(E-E\) bond among non-metals is for nitrogen (N–N is weaker than P–P due to lone pair repulsion in small atoms). Nitrogen has no \(d\)-orbitals and maximum covalency of 4 (e.g., in \(\text{NH}_4^+\), using the lone pair to form a dative bond). Maximum covalency of N \(= 4\).