Question

Which group contains coloured ions out of
1. $C{u}^{2+}$
2. $T{i}^{4+}$
3. $C{o}^{2+}$
4. $F{e}^{2+}$

• A. 1,2,3,4
• B. 1,3,4
• C. 2,3
• D. 1,2

Answer 1

Answer: (B)

Colour of a compound is property of unpaired $d$-electrons.

Ion	$C{u}^{2+}$	$T{i}^{4+}$	$C{o}^{2+}$	$F{e}^{2+}$
Electronic configuration	$3d^9$	$3d^0$	$3d^7$	$3d^6$
No. of unpaired electrons	1	0	3	4

Since $C{u}^{2+},C{o}^{2+}$ and $F{e}^{2+}$ contain unpaired electrons these are coloured ions.