What is Iron?
:''This article is about iron the metal. For the tool called iron, see [[ironing]].'' [[File:Iron lamp.jpg|thumb|A chunk of iron]] '''Iron''' is a [[chemical element]] and a [[metal]]. It is the most common [[chemical element]] on [[Earth]] (by [[mass]]), and the most widely used metal. It makes up much of the [[Earth's core]], and is the fourth most common element in the [[Earth's crust]]. Its [[atomic number]] is 26, because each atom has 26 protons. The metal is used a lot because it is strong and cheap. Iron is the main ingredient used to make [[steel]]. Raw iron is [[Magnet|magnetic]] (attracted to magnets), and its compound [[Iron(II,III) oxide|magnetite]] is [[Magnet|permanently magnetic]]. In some regions iron was used around 1200 BCE. That event is considered the transition from Bronze Age to Iron Age. ==Properties== [[File:Iron(II) oxide.jpg|thumb|alt=|Iron(II) oxide]][[File:Iron(II)-sulfate-heptahydrate-sample.jpg|thumb|alt=|Iron(II) sulfate]] [[File:Iron(III) chloride hexahydrate.jpg|thumb|alt=|Iron(III) chloride]] === Physical properties === Iron is a grey, silvery metal. It is [[magnetic]], though different [[allotropes of iron]] have different magnetic qualities. Iron is easily found, mined and [[Smelting|smelted]], which is why it is so useful. Pure iron is soft and very [[Malleability|malleable]]. === Chemical properties === Iron is reactive. It reacts with most [[acid]]s like [[sulfuric acid]]. It makes [[ferrous sulfate]] when it reacts with sulfuric acid. This reaction with sulfuric acid is used to clean metal. Iron reacts with air and water to make [[rust]]. When the rust flakes off, more iron is exposed allowing more iron to rust. Eventually, the whole piece of iron is rusted away. Other metals like [[aluminum]] do not rust away. Iron can be [[alloy]]ed with [[chromium]] to make [[stainless steel]], which does not rust under most conditions. Iron powder can react with [[sulfur]] to make [[iron(II) sulfide]], a hard black solid. Iron also reacts with the [[halogen]]s to make iron(III)