p Block Elements Part 3

Concept:The hydrides of group 15 elements are $\mathrm{NH_3}$, $\mathrm{PH_3}$, $\mathrm{AsH_3}$, and $\mathrm{SbH_3}$.Their stability, basicity, reducing character, and boiling points vary down the group due to changes in atomic size, bond strength, lone pair availability, and hydrogen bonding.Explanation:A. Stability decreases down the group – Correct.Down the group, atomic size increases, so the $\mathrm{E-H}$ bond becomes weaker and longer.This makes the hydride less stable: $\mathrm{NH_3 > PH_3 > AsH_3 > SbH_3}$.B. Basicity decreases down the group – Correct.Basicity depends on the availability of the lone pair on the central atom.Down the group, the lone pair becomes more diffuse and less able to donate, so basicity decreases: $\mathrm{NH_3 > PH_3 > AsH_3 > SbH_3}$.C. Reducing character increases down the group – Correct.Weaker $\mathrm{E-H}$ bonds down the group allow the hydride to donate hydrogen more easily.Thus, reducing character increases: $\mathrm{NH_3 < PH_3 < AsH_3 < SbH_3}$.D. Boiling point increases down the group – Not generally correct.Although molar mass increases, $\mathrm{NH_3}$ has strong hydrogen bonding, giving it an unusually high boiling point.The trend is not strictly increasing because $\mathrm{NH_3}$ breaks the order.Answer:Statements A, B, and C are correct. D is incorrect.Therefore, the correct option is A (A, B & C only).