JEE Main 2026 — p Block Elements (Group 15, 16, 17 & 18) Question with Solution

The p-block element E forms a binary cation $(E{H}_x{)}^{+}$ with hydrogen and produces a basic mercury(II) amido-iodide precipitate with $K_{2}Hg{I}_4$ in alkaline medium.
This behavior is characteristic of ammonia (NH₃), which forms the ammonium ion $(N{H}_4{)}^{+}$ and reacts with Nessler's reagent ($K_{2}Hg{I}_4$) to form a characteristic brown/yellow precipitate.
Therefore, E is Nitrogen (N), a Group 15 p-block element with electronic configuration $1s^{2}2s^{2}2p^3$.
Nitrogen has a notably high first ionization enthalpy compared to other group 15 elements due to:
Small atomic radius
High effective nuclear charge
Stable half-filled p³ subshell configuration
The first ionization enthalpy of nitrogen is 1402 kJ/mol.