Ncert Exercises & Solutions

A set that contain only isoelectronic ions is -

(a) ${Zn}^{2 +}, {Ca}^{2 +}, {Ga}^{3 +}, {Al}^{3 +}$

(b) $K^{+}, {Ca}^{2 +}, {Sc}^{3 +}, {Cl}^{-}$

(d) ${Ti}^{4 +}, Ar, {Cr}^{3 +}, V^{5 +}$

(b, c)

(a)

{Zn}^{2 +} (30 - 2 = 28), {Ca}^{2 +} = (20 - 2 = 18), {Ga}^{3 +} (31 - 3 = 28), {Al}^{3 +} (13 - 3 = 10) .

These species have different number of electrons and hence are not isoelectronic ions.

(b)

K^{+} (19 - 1 = 18), {Ca}^{2 +} (20 - 2 = 18), {Sc}^{3 +} (21 - 3 = 18), {Cl}^{-} (17 + 1 = 18)

These are all isoelectronic ions since each one of them has 18 electrons.

(c)

P^{3 -} (15 + 3 = 18), S^{2 -} (16 + 2 = 18), {Cl}^{-} (17 + 1 = 18), K^{+} (19 - 1 = 18) .

These are all isoelectronic ions since each one of them has 18 electrons.

(d)

{Ti}^{4 +} (22 - 4 = 18), Ar (18), {Cr}^{3 +} (24 - 3 = 21), V^{5 +} (23 - 5 = 18)