This is an old revision of this page, as edited by Jorge Stolfi (talk | contribs) at 12:42, 2 April 2019 (Starting to create a full iron(II) article about iron in the 2+ oxidation state). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.
Revision as of 12:42, 2 April 2019 by Jorge Stolfi (talk | contribs) (Starting to create a full iron(II) article about iron in the 2+ oxidation state)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)In chemistry, iron(II) refers to the element iron in its +2 oxidation state; meaning an atom of iron that has lost two of its electrons. In ionic compounds (salts), such an atom may occur as a separate cation (positive ion) denoted by Fe.
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 or Fe. The word ferrous is derived from the Latin word ferrum for iron.
Iron(II) atoms may also occur as coordination complexes, such as the polymer iron(II) oxalate dihydrate, [Fe(C2O4)(H2O)2]n or [Fe·C2O2−4·H2O]n; and organometallic compounds, such as the neutral molecule ferrocene, Fe(C2H5)2 or [Fe][C5H−5]2.
Iron is almost always encountered in the oxidation states 0 (as in the metal), +2, or +3. Solid iron(II) salts are relatively stable in air, but in the presence of air and water they tend to oxidize to iron(III) salts that include hydroxide (HO) or oxide (O anions.