Question
Which is correct increasing 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 :
$$Bi < Sb < As < P < N$$
Solution :
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.