In chromyl chloride, the number of d-electrons present on chromium is the same as in:
(Given atomic numbers: Ti = $22$ , V = $23$ , Cr = $24$ , Mn = $25$ , Fe = $26$ )

Question

In chromyl chloride, the number of d-electrons present on chromium is the same as in: (Given atomic numbers: Ti = 22, V = 23, Cr = 24, Mn = 25, Fe = 26)

Accepted Answer

Given: Chromium in chromyl chloride is in $\text{CrO}_2\text{Cl}_2$ .

Find: Which species has the same number of $d$ -electrons as chromium in chromyl chloride.

For $\text{CrO}_2\text{Cl}_2$ , let the oxidation state of chromium be $x$ .

x + 2(-2) + 2(-1) = 0

So,

x - 4 - 2 = 0

x = +6

Chromium has atomic number $24$ , so its ground-state configuration is

\text{Cr} = [\text{Ar}]\,3d^5 4s^1

Therefore,

\text{Cr}^{6+} = [\text{Ar}]\,3d^0 4s^0

So chromium has zero $d$ -electrons in chromyl chloride.

Now check manganese in $\text{Mn (VII)}$ . Manganese has atomic number $25$ and configuration

\text{Mn} = [\text{Ar}]\,3d^5 4s^2

Hence,

\text{Mn}^{7+} = [\text{Ar}]\,3d^0 4s^0

So manganese in oxidation state $+7$ also has zero $d$ -electrons.

Therefore, the number of $d$ -electrons is the same in chromium of chromyl chloride and Mn (VII). The correct option is D.

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