Ferrous

In chemistry, iron(II) refers to the element iron in its +2 oxidation state. The adjective ferrous or the prefix ferro- is often used to specify such compounds, as in ferrous chloride for iron(II) chloride (FeCl₂). The adjective ferric is used instead for iron(III) salts, containing the cation Fe³⁺. The word ferrous is derived from the Latin word ferrum, meaning "iron".

In ionic compounds (salts), such an atom may occur as a separate cation (positive ion) abbreviated as Fe²⁺, although more precise descriptions include other ligands such as water and halides. Iron(III) centres occur in coordination complexes, such as in the anion ferrocyanide, [Fe(CN)₆]⁴⁻, where six cyanide ligands are bound the metal centre; or, in organometallic compounds, such as the ferrocene [Fe(C₂H₅)₂], where two cyclopentadienyl anions are bound to the Fe^II centre.