What is a Fe2 electron configuration?

The electron configuration for Fe2+ is 1s2 2s2 2p6 3s2 3p6 3d6. Due to its plus two charge, the electron configuration for Fe2+ contains two fewer electrons than the electron configuration for Fe, which is 1s2 2s2 2p6 3s2 3p6 3d6 4s2.

The Fe2+ ion does not contain any electrons in the 4s-orbital, instead ending after completely filling the 3d-orbital. According to UC Davis ChemWiki, the first number listed for each configuration stands for the energy level. The letter stands for the type of orbital. The second letter, typically written in superscript, indicates how many electrons are present in the orbital for the particular electron configuration expressed.