Fe2

Fe2 is a designation that can refer to different iron-containing species depending on the context. It is not a single compound with a fixed formula, but rather a shorthand used in discussions of gas-phase species, aqueous chemistry, and mineralogy to indicate iron in particular forms or oxidation states.

As a diatomic molecule, Fe2 denotes a neutral molecule composed of two iron atoms. Fe2 has been observed in high-temperature gas phases and laboratory plasmas, and it has been the subject of spectroscopic studies aimed at understanding its electronic states and bonding. In such contexts, Fe2 is typically short-lived and not present under ordinary, ambient conditions.

As a ferrous ion, Fe2+ represents iron in the +2 oxidation state. In solution and in minerals, Fe2+ is common and participates in redox reactions and complex formation. It can be oxidized to Fe3+ under oxidizing conditions and can form a variety of coordination compounds with ligands, influencing its reactivity, color, and solubility. In biological systems, Fe2+ plays roles in processes such as electron transfer and enzyme activity, though it can be sensitive to oxidation.

In mineralogy and solid-state chemistry, Fe2+ is used to describe iron occupying lattice sites in the +2 state, often alongside Fe3+ in mixed-valence minerals (for example, in magnetite, Fe3O4). The exact interpretation of Fe2 depends on the surrounding context, including charge balance, mineral structure, and accompanying chemical information. Readers should infer the intended meaning from related data and notation.