Iron ( /ˈaɪ.ərn/ or /ˈaɪərn/) is a chemical element with the symbol Fe (Latin: ferrum) and atomic number 26. It is a metal in the first transition series. It is the most common element in the whole planet Earth, forming much of Earth’s outer and inner core, and it is the fourth most common element in the Earth’s crust. It is produced in abundance as a result of fusion in high-mass stars, where the production of nickel-56 (which decays to iron) is the last nuclear fusion reaction that is exothermic, becoming the last element to be produced before collapse of a supernova leads to events that scatter the precursor radionuclides of iron into space
This article is about the chemical element. For other uses, see Iron (disambiguation).