Which of the following electron configurations is correct for iron,(atomic number :26)?

Options

A. `1s^(2), 2s^(2)2p^(6), 3s^(2)3p^(6) 3d^(5)`
B. `1s^(2), 2s^(2)2p^(6), 3s^(2)3p^(6), 4s^(2), 3d^(5)`
C. `1s^(2), 2s^(2)2p^(6), 3s^(2)3p^(6), 4s^(2), 3d^(7)`
D. `1s^(2), 2s^(2) 2p^(6), 3s^(2)3p^(6)3d^(6), 4s^(2)`

Answer

D

Explanation

(d) Firstly the electrons are filled in increasing order of energy and then rearrange the subshells in increasing order as
`._(26)Fe=1s^(2), 2s^(2) 2p^(6), 3s^(2) 3p^(6)3d^(6),4s^(2)`