The electronic structure of iron.

Fe is iron, an element with atomic number 26, which means there are 26 protons in its nucleus, and 26 electrons revolve around the nucleus.
Ar (Fe) = 56, which means the number of neutrons in the nucleus is 56 – 26 = 30.
This is an element of the 4th period, which means that the electrons are located at four electronic levels.
Period 4 is a large period, and Fe is in a side subgroup, which means that it has 2 electrons at the last electronic level, and valence electrons are added to d – sublevel 3 of level.
Electronic formula of iron:
1s2 2s22p6 3s23p63d6 4s2.