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Ferrous
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<p>In <a href="/facts/Chemistry/SrNqkGVm">chemistry</a>, iron(II) refers to the <a href="/facts/Chemical_element/0jducgWD">element</a> <a href="/facts/Iron/DkICCKIC">iron</a> in its +2 <a href="/facts/Oxidation_number/W53W6s6V">oxidation state</a>. The adjective <i>ferrous</i> or the prefix <i>ferro-</i> is often used to specify such compounds, as in <i>ferrous chloride</i> for <a href="/facts/Iron(II)_chloride/FNFq9GRl">iron(II) chloride</a> (FeCl2). The adjective <i><a href="/facts/Ferric/TMrSskIt">ferric</a></i> is used instead for <a href="/facts/Iron(III)/TMrSskIt">iron(III)</a> salts, containing the cation Fe3+. The word <i>ferrous</i> is derived from the <a href="/facts/Latin/pM3Kge85">Latin</a> word <i>ferrum</i>, meaning "iron". </p><p>In <a href="/facts/Salt_(chemistry)/lsSKwGpn">ionic compounds</a> (salts), such an atom may occur as a separate <a href="/facts/Cation/wrbwhF3z">cation</a> (positive ion) abbreviated as Fe2+, although more precise descriptions include other ligands such as water and halides. Iron(II) centres occur in <a href="/facts/Coordination_complex/1tCyeQUm">coordination complexes</a>, such as in the <a href="/facts/Anion/wrbwhF3z">anion</a> <a href="/facts/Ferrocyanide/ccDHxjNN">ferrocyanide</a>, [Fe(CN)6]4−, where six <a href="/facts/Cyanide/t0o8FMKI">cyanide</a> ligands are bound the metal centre; or, in <a href="/facts/Organometallic_compound/bhqFz2P0">organometallic compounds</a>, such as the <a href="/facts/Ferrocene/jKtu9Cp8">ferrocene</a> [Fe(C2H5)2], where two <a href="/facts/Cyclopentadienyl/2cw59tjx">cyclopentadienyl</a> anions are bound to the FeII centre. </p>