The p-block element E forms a binary cation (EHx)+ with hydrogen and produces a basic mercury(II) amido-iodide precipitate with K2HgI4 in alkaline medium.
This behavior is characteristic of ammonia (NH₃), which forms the ammonium ion (NH4)+ and reacts with Nessler's reagent (K2HgI4) to form a characteristic brown/yellow precipitate.
Therefore, E is Nitrogen (N), a Group 15 p-block element with electronic configuration 1s22s22p3.
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.