The number of unpaired d-electrons in $\left[\mathrm{Co}\left(\mathrm{H}_{2}\mathrm{O}\right)_{6}\right]^{3+}$ is

JEE Main · 2024 · 04 Apr 2024 · Shift 2 · Coordination Compounds

The number of unpaired d-electrons in

[Co (H_{2} O)_{6}]^{3 +}

(A)4
(B)2
(C)0✓ Correct
(D)1

Answer: (C)

Solution

C o^{3 +}

has a

d^{6}

configuration. Despite

H_{2} O

being only a moderately strong field ligand in general, the high charge on

C o^{3 +}

increases the crystal field splitting enough that

[C o (H_{2} O)_{6}]^{3 +}

is experimentally low-spin:

t_{2 g}^{6} e_{g}^{0}

. All six d-electrons are paired in the

t_{2 g}

set, so there are 0 unpaired electrons.

Structure Electronic configuration diagram — Electronic configuration diagram

JEE Main · 2024 · 04 Apr 2024 · Shift 2 · Single correct option

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