Electron configuration of iron

Iron (Fe) has an electronic configuration of [Ar] 3d⁶ 4s².

The 26 electrons in iron. These electrons are distributed as follows among the numerous orbitals, shells, and subshells:

1s subshell

The 1s subshell is the only subshell present in the first shell (n = 1). The 1s orbital, which makes up this subshell, has one orbital and has a capacity of two electrons.
For iron, there are two electrons in the 1s orbital.

2s subshell

The 2s subshell and the 2p subshell are the two subshells that make up the second shell (n = 2). The 2s orbital, which is the only orbital in the 2s subshell and can hold two electrons, is also present.
This orbital in iron has two electrons in it. The 3 orbitals that make up the 2p subshell are 2px, 2py, and 2pz.
There are a total of 6 electrons in the 2p subshell of iron, with each of these orbitals having a maximum capacity of 2 electrons.

3s subshell

The 3s subshell and the 3p subshell are encountered as we get to the third shell (n = 3).
The 3s subshell, like the previous shells, has a single 3s orbital that can hold two electrons, as it does for iron.
On the other hand, the 3p subshell is made up of three orbitals: 3px, 3py, and 3pz.
The 3p subshell of iron may accommodate a maximum of 6 electrons, or 2 electrons in each of these orbitals.

3d subshell:

The third shell’s third subshell is the next stop on our journey. Five orbitals make up the 3d subshell: 3dxy, 3dyz, 3dz2, 3dxz, and 3dx2-y2.
Only six of the three-dimensional orbitals in iron are filled with electrons, despite the fact that all of these orbitals have a maximum capacity of ten electrons.

4s subshell

The 4s subshell is located in the fourth shell (n = 4), which is where we move after that.
There is just one 4s orbital in this subshell, and it can accommodate two electrons.
This orbital in iron has two electrons in it.

Note

iron (Fe) has an electronic configuration of [Ar] 3d⁶ 4s².

which means that there are 6 electrons in the 3d subshell, 2 electrons in the 4s subshell, and the remaining electrons are split between the 1s, 2s, 2p, 3s, and 3p subshells.

Table of electronic configuration of iron

Shell	Subshell	Orbitals	Electrons
1	1s	1s	2
2	2s	2s	2
	2p	2px, 2py, 2pz	6
3	3s	3s	2
	3p	3px, 3py, 3pz	6
4	3d	3dxy, 3dyz, 3dz2, 3dxz, 3dx2-y2	6
5	4s	4s	2

Electron configuration of iron
By: Prof. Dr. Fazal Rehman Shamil | Last updated: February 3, 2024