View source for 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 [[magnetic]] (attracted to magnets), and its compound [[magnetite]] is [[permanent 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) [[halide]]s, like [[iron(III) chloride]]. Iron reacts with the [[hydrohalic acid]]s to make iron(II) halides like [[iron(II) chloride]].

=== Chemical compounds ===
Iron makes [[chemical compound]]s with other elements. Normally the other element [[oxidation|oxidizes]] iron. Sometimes two electrons are taken and sometimes three. Compounds where iron has two electrons taken are called [[ferrous]] compounds. Compounds where iron has three electrons taken are called [[ferric]] compounds. Ferrous compounds have iron in its +2 [[oxidation state]]. Ferric compounds have iron in its +3 [[oxidation state]]. Iron compounds can be black, brown, yellow, green, or purple.

Ferrous compounds are weak [[reducing agent]]s. Many of them are green or blue. The most common ferrous compound is ferrous sulfate.

Ferric compounds are [[oxidizing agent]]s. Many of them are brown. The most common ferric compound is [[ferric oxide]], the same thing as rust. One reason why iron rusts is because ferric oxide is an oxidizing agent. It oxidizes iron, rusting it even under paint. That is why if there is a small scratch in the paint, the whole thing can rust.

====Iron(II) compounds====
Compounds in the +2 oxidation state are weak [[reducing agent]]s. They are normally light colored. They [[chemical reaction|react]] with [[oxygen]] in [[air]]. They are also known as [[ferrous]] compounds.
*[[Iron(II) sulfide]], a shiny chemical that reacts with [[acid]]s to release [[hydrogen sulfide]], found in the ground
*[[Iron(II) sulfate]], a blue-green [[crystalline]] chemical made by reacting [[sulfuric acid]] with [[steel]], used to [[reduction (chemistry)|reduce]] poisons like [[chromate]] in [[concrete]]
*[[Iron(II) chloride]], a pale green crystalline chemical made by reacting [[hydrochloric acid]] with [[steel]]
*[[Iron(II) hydroxide]], a dark green powder made by [[electrolysis|electrolyzing]] [[water]] with an iron [[anode]], reacts with [[oxygen]] and turns brown
*[[Iron(II) oxide]], black, flammable, rare

====Mixed oxidation state====
These compounds are rare; only one is common. They are found in the ground.
*[[Iron(II,III) oxide]], a black [[mineral]], used as [[ore]] of iron, contains iron in the +2 and +3 [[oxidation state]].

====Iron(III) compounds====
Compounds in the +3 oxidation state are normally brown. They are [[oxidizing agent]]s. They are [[corrosive]]. They are also known as [[ferric]] compounds.
*[[Iron(III) oxide]], [[rust]], red-brown, dissolves in [[acid]]
*[[Iron(III) chloride]], poisonous and [[corrosive]], dissolves in water to make dark brown [[acid]]ic [[solution]]. Made by [[chemical reaction|reacting]] iron with [[hydrochloric acid]] and an [[oxidizing agent]]
*[[Iron(III) nitrate]], light purple, corrosive, used in etching
*[[Iron(III) sulfate]], rare, light brown, dissolves in water. Made by reacting iron with [[sulfuric acid]] and an [[oxidizing agent]].

== Where iron is found ==
There is a lot of iron in the [[universe]] because it is the end point of the [[nuclear reaction]]s in large [[stars]]. It is the last element to be produced before the violent collapse of a [[supernova]] scatters the iron into space.

The metal is the main ingredient in the [[Earth's core]]. Near the surface it is found as a [[ferrous]] or [[ferric]] compound. Some [[meteorite]]s contain iron in the form of rare minerals. Normally iron is found as [[hematite]] [[ore]] in the ground, much of which was made in the [[Great Oxygenation Event]]. Iron can be extracted from the ore in a [[blast furnace]]. Some iron is found as [[magnetite]].

There are iron compounds in meat. Iron is an essential part of the [[hemoglobin]] in [[red blood cell]]s.

== Making iron ==
[[File:Engelsberg-Huettenwerk-01.jpg|thumb|Blast furnace]]
Iron is made in large factories called ''ironworks'' by reducing hematite with [[carbon]] (coke). This happens in large containers called [[blast furnace]]s. The blast furnace is filled with iron ore, coke and limestone. A very hot blast of air is blown in, where it causes the coke to burn. The extreme heat makes the carbon react with iron ore, taking off the [[oxygen]] from iron oxides, and making [[carbon dioxide]]. The carbon dioxide is a gas and it leaves the mix. There is some [[sand]] in with the iron. The limestone, which is made of [[calcium carbonate]], turns into [[calcium oxide]] and carbon dioxide when the limestone is very hot. The calcium oxide reacts with the sand to make a liquid called a [[wikt:slag|slag]]. The slag is drained, leaving only the iron. The reaction will leave pure liquid iron in the blast furnace, where it can be shaped and hardened after cooling down. Almost all ironworks are today part of [[steel mill]]s, and almost all iron is made into [[steel]].

There are many ways to work iron. Iron can be hardened by heating a piece of metal and splashing it into cold water. It can be softened by heating it and allowing it to slowly cool. It can also be stamped by a heavy press. It can be pulled into wires. It can be rolled to make sheet metal.

In the [[United States]], much of the iron was taken from the ground in [[Minnesota]] and then sent by ship to [[Indiana]] and [[Michigan]] where it was made into [[steel]].

==Uses==
=== As a metal ===
[[File:Znamensk most.jpg|thumb|right|200px|A [[bridge]] made out of iron]]
Iron is used more than any other metal. It is strong and cheap. It is used to make buildings, bridges, nails, screws, pipes, girders, and towers.

Iron is not very reactive, so it is both easy and cheap to extract from ores. It is very strong once made into steel, and is used to reinforce [[concrete]].

There are different types of iron. [[Cast iron]] is iron made by the way described above in the article. It is hard and [[wikt:brittle|brittle]]. It is used to make things like [[wikt:storm drain|storm drain]] covers, manhole covers, and [[engine]] blocks (the main part of an engine).

[[Steel]] is the most common form of iron. Steels come in several forms. [[Mild steel]] is steel with a low percentage of carbon. It is soft and easily bent, but it does not crack easily. It is used for nails and wires. [[Carbon steel]] is harder but more brittle. It is used in tools.

There are other types of steel. [[Stainless steel]], because of the chromium content, is rust resistant, and [[nickel]]-iron alloys can remain strong at high temperatures. Other steels can be very hard, depending on the [[alloy]]s added.

[[Wrought iron]] is easily shaped and used to make fences and chains.

Very pure iron is soft, and can rust (oxidize) easily. It is also fairly reactive.

===As compounds===
Iron compounds are used for several things. Iron(II) chloride is used to make water clean. [[Iron(III) chloride]] is also used. Iron(II) sulfate is used to [[reduction (chemistry)|reduce]] [[chromate]]s in [[cement]]. Some iron compounds are used in vitamins.

== Nutrition ==
Iron deficiency is the most common [[nutritional deficiency]] in the world.<ref>{{cite journal|last1=Centers for Disease Control and Prevention|title=Iron deficiency – United States, 1999–2000.|journal=MMWR|date=2002|volume=51|issue=40|pages=897–9|pmid=12418542}}</ref><ref>{{cite book|first1=Robert C.|last1=Hider|first2=Xiaole|last2=Kong|editor=Astrid Sigel, Helmut Sigel and Roland K. O. Sigel|title=Interrelations between Essential Metal Ions and Human Diseases|series=Metal Ions in Life Sciences|volume=13|year=2013|publisher=Springer|pages=229–294|chapter=Chapter 8. Iron: Effect of Overload and Deficiency|doi=10.1007/978-94-007-7500-8_8|pmid=24470094}}</ref><ref>{{cite book |last1=Dlouhy |first1=Adrienne C. |last2=Outten|first2=Caryn E. |editor1-first=Lucia (Ed.) |editor1-last=Banci |series=Metal Ions in Life Sciences |volume=12 |chapter= Chapter 8.4 Iron Uptake, Trafficking and Storage|title=Metallomics and the Cell |year=2013 |pages=241–278 |publisher=Springer |isbn=978-94-007-5560-4|doi=10.1007/978-94-007-5561-1_8|pmid=23595675 |pmc=3924584 }} electronic-book {{ISBN|978-94-007-5561-1}} {{issn|1559-0836}} electronic-{{issn|1868-0402}}</ref>

Human bodies need iron to help oxygen get to our muscles, because it is at the heart of some essential [[macromolecule]]s such as [[hemoglobin]]. Many [[cereal]]s have some added iron (the [[Chemical element|element]] ''metal'' iron).<ref>{{cite web|url=http://www.ars.usda.gov/IS/AR/archive/may03/iron0503.htm|title=Testing the fortitude of iron in cereals|publisher=[[United States Department of Agriculture]]|accessdate=2010-01-29}}</ref><ref>Adams, Cecil. ''Return of the Straight Dope''. New York: Ballantine Books, 1994</ref> It is added to cereal in the form of tiny metal filings. It is even possible to see the slivers sometimes by taking an extremely strong [[magnet]] and putting it into the box. The magnet will attract these pieces of iron. Eating these small metal [[wikt:shaving|shavings]] are not harmful to our body.<ref>Felton, Bruce. ''One of a Kind''. New York: William Morrow and Co., 1992</ref>

Iron is most available to the body when added to [[amino acid]]s – iron in this form is ten to fifteen times more digestible than than it is as an element.<ref name="pmid11377130">{{cite journal |author=Pineda O. & Ashmead H.D. |title=Effectiveness of treatment of iron-deficiency anemia in infants and young children with ferrous bis-glycinate chelate |url=https://archive.org/details/sim_nutrition_2001-05_17_5/page/381 |journal=Nutrition |volume=17 |issue=5 |pages=381–4 |year=2001 |pmid=11377130| doi = 10.1016/S0899-9007(01)00519-6|issn=0899-9007 }}</ref> Iron is also found in [[meat]], for example [[steak]]. Iron provided by [[diet supplement]]s is in the form of a chemical, such as [[Iron(II) sulfate]], which is cheap and is absorbed well. The body will not take up more iron than it needs, and it usually needs very little. The iron in [[red blood cell]]s is recycled by a system which breaks down old cells. Loss of blood by injury or [[parasite]] infection may be more serious.<ref>Andrews N.C. 2000. Disorders of iron metabolism. ''New England Journal of Medicine''. Related correspondence, published in NEJM '''342''':1293-1294.</ref>

== Toxicity ==
Iron is [[wikt:toxic|toxic]] when large amounts are taken into the body. When too many iron pills are taken, people (especially children) get sick. Also, there is a [[genetic disorder]] which damages the regulation of iron levels in the body.

==Related pages==
*[[Allotropes of iron]]
*[[Iron compounds]]
*[[Iron Age]]

==References==
<references/>

{{Periodic Table}}
{{authority control}}
[[Category:Iron| ]]
[[Category:Metallurgy]]