Iron(II) ion
Charge: 2+ · Type: Cation · Molar mass: 55.845 g/mol
Made of: iron
How it forms
Iron first loses its two 4s electrons to form Fe2+. This ion can be further oxidized to Fe3+, which is why iron(II) solutions slowly turn yellow-brown in air as the iron(II) oxidizes.
Naming note
Fe2+ is named iron(II), with the Roman numeral showing the 2+ charge. The older name ferrous ion is still used in some industries.
Examples in compounds
Iron(II) sulfate
Iron(II) chloride
Iron(II) oxide