Paper: CSIR-NET June 2018 · Subject: Inorganic Chemistry · Chapter: Main Group Elements · Topic: Main Group Elements – General · Marks: 2 · Difficulty: Medium
Consider following statements: I: $\mathrm{AsCl}_{5}$ is thermally less stable than $\mathrm{PCl}_{5}$. II: Size of As is more than that of P. choose correct answer from the following
(a)Statements I and II are true and II is the correct explanation of I.
(b)Statements I and II are true but II is not the correct explanation of I.
(c)Statement I is true and statement II is false.
(d)Both the statements I and II are false.
Answer
Answer: B ✓ checked by 4AB · confidence high
Explanation
AsCl₅ is indeed less stable than PCl₅, and As is larger than P, but the reason is the d-block contraction: the poorly shielding 3d¹⁰ shell makes the As 4s pair harder to use (alternation effect), not the size.