A ' p '-block element ( E ) and hydrogen form a binary cation ( EH _ x )^ + , while EH _ 3 on treatment with K _ 2 HgI _ 4 in alkaline medium gives a precipitate of basic mercury(II)amido-iodine. Given below are first ionisation enthalpy values ( kJ mol ^ -1 ) for first element each from group 13, 14, 15 and 16. Identify the correct first ionisation enthalpy value for element E.
B. 1402
The p-block element E forms a binary cation (EH_x)^+ with hydrogen and produces a basic mercury(II) amido-iodide precipitate with K_2HgI_4 in alkaline medium. This behavior is characteristic of ammonia (NH₃), which forms the ammonium ion (NH_4)^+ and reacts with Nessler's reagent (K_2HgI_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.
Related: Chemistry — p Block Elements (Group 15, 16, 17 & 18) · All PYQ Banks