Explanation

(c)
$Fe(26) = 1s^{2},2s^{2}2p^{6},3s^{2}3p^{6}3d^{6},4s^{2}$
[image:2_image23.emf]
Hence, it has 4 unpaired electrons.
$Fe^{2 +} = 1s^{2},2s^{2}2p^{6},3s^{2}3p^{6}3d^{6},4s^{0}$
∴ It also has 4 unpaired electrons.
$Fe^{3 +} = 1s^{2},2s^{2}2p^{6},3s^{2}3p^{6}3d^{5},4s^{0}$
[image:2_image24.emf]
Hence, it has 5 unpaired electrons.