Question
Which of the following configuration is correct for iron?
A.
$$1{s^2},\,2{s^2}2{p^6},3{s^2}3{p^6}3{d^5}$$
B.
$$1{s^2},2{s^2}2{p^6},3{s^2}3{p^6},4{s^2},3{d^5}$$
C.
$$1{s^2},2{s^2}2{p^6},3{s^2}3{p^6},4{s^2},3{d^7}$$
D.
$$1{s^2},2{s^2}2{p^6},3{s^2}3{p^6}3{d^6},4{s^2}$$
Answer :
$$1{s^2},2{s^2}2{p^6},3{s^2}3{p^6}3{d^6},4{s^2}$$
Solution :
Firstly the electrons are filled in increasing order of energy and then rearrange the subshells in increasing order as
$$_{26}Fe = 1{s^2},2{s^2}2{p^6},3{s^2}3{p^6}3{d^6},4{s^2}$$