Ncert Exercises & Solutions

8.18 Predict which of the following will be coloured in aqueous solution? Ti³⁺, V³⁺, Cu⁺, Sc³⁺, Mn²⁺, Fe³⁺ and Co²⁺. Give reasons for each.

Step 1:

Only that ions show colour which has unpaired electrons in its d orbital. If ions configuration is 3d⁰ or 3d¹⁰ then it will not colour.

Step 2:

Element	Atomic Number	Ionic State	Electronic configuration in ionic state
Ti	22	Ti $^{3 +}$	$[A r] 3 d^{1}$
V	23	V $^{3 +}$	$[A r] 3 d^{2}$
Cu	29	Cu $^{+}$	$[A r] 3 d^{10}$
Sc	21	Sc³⁺	[Ar]3d⁰
Mn	25	Mn $^{2 +}$	$[A r] 3 d^{5}$
Fe	26	Fe $^{3 +}$	$[A r] 3 d^{5}$
Co	27	Co $^{2 +}$	$[A r] 3 d^{7}$

From the above table, it can be easily observed that only Sc $^{3 +}$ and Cu⁺ has an empty d-orbital or completely filled d orbital.
Hence, they will not show d-d transition and not impart any colour.

NEET Information

courses

Company

Botany Questions

Chemistry Questions

Physics Questions

Zoology Questions