1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²

This means that iron has:

- 2 electrons in the first shell (n=1)

- 8 electrons in the second shell (n=2)

- 14 electrons in the third shell (n=3)

- 2 electrons in the fourth shell (n=4)