The d-electronic configuration of $\left[\mathrm{CoCl}_{4}\right]^{2-}$ in tetrahedral crystal field is $e^{m} t_{2}{ }^{n}$. Sum of ' $m$ ' and 'number of unpaired electrons is ______.

JEE Main · 2023 · 24 Jan 2023 · Shift 1 · Coordination Compounds

The d-electronic configuration of

[CoCl_{4}]^{2 -}

in tetrahedral crystal field is

e^{m} t_{2}^{n}

. Sum of '

m

' and 'number of unpaired electrons is ______.

Answer: 7

Solution

[CoC l_{4}]^{2 -}

the metal is cobalt(II) with a

3 d^{7}

configuration, and chloride is a weak-field ligand, so the complex is high-spin. In a tetrahedral field the

e

set lies below the

t_{2}

set, and the seven electrons fill as

e^{4} t_{2}^{3}

, so

m = 4

. The three

t_{2}

electrons stay unpaired, giving three unpaired electrons, and the sum of

m

and the number of unpaired electrons is seven.

JEE Main · 2023 · 24 Jan 2023 · Shift 1 · Integer answer

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