JEE Main · 2025 · 04 Apr 2025 · Shift 1 · d and f Block Elements

Pair of transition metal ions having the same number of unpaired electrons is :

Answer: (A)

Solution

The count of unpaired electrons follows from the

3 d

configuration of each ion.

V^{2 +}

3 d^{3}

with three unpaired electrons and

C o^{2 +}

3 d^{7}

, which also leaves three unpaired, so this pair agrees. The others differ:

T i^{2 +}

(

3 d^{2}

) has two against the three of

C o^{2 +}

F e^{3 +}

(

3 d^{5}

) has five against the four of

C r^{2 +}

(

3 d^{4}

), and

T i^{3 +}

(

3 d^{1}

) has one against the five of

M n^{2 +}

(

3 d^{5}

). The pair having the same number of unpaired electrons is

V^{2 +}

and

C o^{2 +}

JEE Main · 2025 · 04 Apr 2025 · Shift 1 · Single correct option