Question

Which is correct order of their tendency of the given elements to form $M^{3-}$ ion$?$

• A. $Bi>Sb>As>P>N$
• B. $Bi<Sb<As<P<N$
• C. $N<P<Sb<Bi<As$
• D. $Bi>Sb\sim N\sim P>As$

Answer 1

The correct option is B $Bi<Sb<As<P<N$

As we Know, on moving down the group, the stability of $-3$ oxidation state decreases.
This is due to the following reasons.
(i) On descending a group the size of the atom or ion increases. As a result, attraction of the nucleus per newly added electron decreases.
(ii) A large anion cannot fit easily into lattice of a small cation. (iii) As the negative charge on the ion increases, it becomes more and more susceptible to polarisation.