The Latin term ferrous refers to the element iron. In chemistry jargon, ferrous refers to an iron atom with a charge of +2, whereas a ferric ion has a charge of +3. In the human body, iron is essential for the production of hemoglobin, the main oxygen transport protein.
On the periodic table, iron is element number 26. Iron is a transition metal, meaning it is not as reactive as elements like sodium or potassium. Although iron is one of the most abundant elements in Earth's crust, free iron is uncommon; most iron occurs in compounds like iron oxide, which is more familiar to people as rust.