EisenII

EisenII, or iron(II), denotes iron in the divalent oxidation state (+2) in chemical compounds. In English, the term is commonly written as iron(II) and is also known by the traditional name ferrous iron. The designation contrasts with iron(III) (ferric iron), where iron has a +3 oxidation state.

In aqueous solutions, Fe2+ forms aquated ions that are typically pale green and readily coordinate with water and other ligands. The Fe2+ ion is susceptible to oxidation by oxygen, converting to Fe3+ (ferric iron) and often precipitating as hydroxides or forming oxides under neutral to basic conditions. The iron(II)/iron(III) redox couple plays a central role in many biological and environmental processes.

Iron(II) occurs naturally in several minerals, such as siderite (FeCO3) and in various ferrous salts used in chemistry. In mixed-valence minerals like magnetite (Fe3O4), iron exists in both +2 and +3 oxidation states. Ferrous compounds are typically less stable in air than their ferric counterparts, especially in solution, where they may oxidize to Fe3+.

Biologically, iron(II) is important in oxygen transport and electron transfer. In hemoglobin and myoglobin, iron cycles between Fe2+ and Fe3+ during oxygen binding and release. Iron(II) also features in various enzymes and iron-sulfur clusters critical to cellular metabolism.

Applications and safety notes: ferrous salts such as ferrous sulfate are used therapeutically as iron supplements but can cause gastrointestinal irritation and toxicity in excess. Proper handling requires awareness of oxidation sensitivity and the potential for environmental and biological redox reactions.