$Fe$ এবং $Fe^{2+}$ এর ইলেকট্রন বিন্যাস যথাক্রমে-

$[\mathrm{Ar}] 3 \mathrm{~d}^{6} 4 \mathrm{~s}^{0},[\mathrm{Ar}] 3 \mathrm{~d}^{4} 4 \mathrm{~s}^{0}$

$[\mathrm{Ar}] 3 \mathrm{~d}^{6} 4 \mathrm{~s}^{2},[\mathrm{Ar}] 3 \mathrm{~d}^{6} 4 \mathrm{~s}^{0}$

$[\mathrm{Ar}] 3 \mathrm{~d}^{5} 4 \mathrm{~s}^{2},[\mathrm{Ar}] 3 \mathrm{~d}^{5}$

$\lceil\operatorname{Ar}\rceil 3 d^{4} 4 s^{2},\lceil\operatorname{Ar}\rceil 3 d^{4} 4 s^{0}$