JEE Main 2026 Apr 5 Shift 2, Chemistry Q21: Colour, Magnetism And Stability Of Co-ordination Compounds

JEE Main2026Apr 5, Shift 2Chemistry

The total number of unpaired electrons present in the $d^{3}$ , $d^{4}$ (low spin), $d^{5}$ (high spin), $d^{6}$ (high spin) and $d^{7}$ (low spin) octahedral complex systems is ____.

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Solution

For an octahedral field, fill $t_{2 g}$ before $e_{g}$ in low spin; in high spin obey Hund's rule before pairing.

$d^{3}$ : $t_{2 g}^{3} e_{g}^{0} \Rightarrow$ 3 unpaired.

$d^{4}$ (LS): $t_{2 g}^{4} e_{g}^{0} \Rightarrow$ 2 unpaired.

$d^{5}$ (HS): $t_{2 g}^{3} e_{g}^{2} \Rightarrow$ 5 unpaired.

$d^{6}$ (HS): $t_{2 g}^{4} e_{g}^{2} \Rightarrow$ 4 unpaired.

$d^{7}$ (LS): $t_{2 g}^{6} e_{g}^{1} \Rightarrow$ 1 unpaired.

Sum $= 3 + 2 + 5 + 4 + 1 = 15$ .

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JEE Main 2026 Apr 5 Shift 2, Chemistry Q21: Colour, Magnetism And Stability Of Co-ordination Compounds

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