An ion (/ˈaɪən, -ɒn/) is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving the atom a net positive or negative electrical charge.

see Ion channel

Fe2+ refers to the ferrous ion, which is a positively charged ion of iron with a 2+ charge. It is a divalent cation and has two electrons that can be donated to form chemical bonds.

Ferrous ions are commonly found in various biological and environmental systems. In the human body, ferrous ions are important for various cellular functions, including oxygen transport, energy production, and DNA synthesis. They are a component of the heme group in hemoglobin, which is responsible for binding and transporting oxygen in red blood cells.