Chemistry - Complete d-block Question with Solution | TestHub

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

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

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

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

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

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

so $Z$ for $M=26$ and $M$ is $Fe.$