Iron is element number 26 on the periodic table. This means an iron atom contains 26 protons in its nucleus. Chemists refer to the number of protons in an atom's nucleus as that element's atomic number.
The atomic number determines an atom's elemental identity. Neutral iron atoms contain 26 electrons, whose equal but opposite charges balance the positive charges of the protons. Iron atoms lose two or three electrons when they come into contact with oxygen and other non-metals. As a result, most of the iron in Earth's crust exists as compounds of iron oxide rather than elemental iron. While iron is abundant in the crust, the bulk of Earth's iron is trapped in the planet's core, which is composed of a solid metal ball surrounded by a liquid metal outer core. The structure of Earth's core along with its spin is thought to give rise to the planet's magnetic field.