Q16 / 90 · JEE Main 2021 (01 Sep Shift 2) · Chemistry

Identify the element for which electronic configuration in $+ 3$ oxidation state is $[Ar] 3 d^{5} :$

Solution

${}_{26}{Fe}^{3 +} = 3 d^{5} 4 s^{0}$

$27 {Co}^{3 +} = 3 d^{6} 4 s^{0}$

${}_{24}{Cr}^{3 +} = 3 d^{3} 4 s^{0}$

$25 {Mn}^{3 +} = 3 d^{4} 4 s^{0}$

$M^{+ 3} = [18 Ar] 3 d^{5} 4 s^{0}$

$M = [{}_{18}{Ar}] 3 d^{6} 4 s^{2}$

so $Z$ for $M = 26$ and $M$ is $F e .$

Hence, the correct answer is option: 'D'.