What is the form of iron known as ferrous iron?

Ferrous iron refers specifically to the divalent state of iron (Fe²⁺), which is capable of being dissolved in water. In this form, it is more soluble and more readily available for biological uptake by plants and microorganisms compared to its oxidized counterpart, ferric iron (Fe³⁺). This solubility is crucial in various environmental contexts, particularly in aquatic systems where iron can play a significant role in nutrient cycling and water quality.

The other forms mentioned—oxidized, precipitated, and oxidative—do not accurately describe ferrous iron. The oxidized form typically refers to ferric iron, which is not dissolved under most conditions, but rather tends to precipitate or form insoluble compounds at higher pH levels. Precipitated iron refers to iron that has combined with other elements or compounds, resulting in a solid form that is no longer dissolved in water. Oxidative may imply a reaction involving oxygen, but does not correlate directly with the characteristics of ferrous iron itself. Thus, it is the dissolved form of ferrous iron that aligns with the definition and properties of this specific state of iron.