What is Nickel?
{{about|the metal|the United States 5 cent coin|nickel (coin)}} [[File:Nickel chunk.jpg|thumb|A chunk of nickel metal]] '''Nickel''' ([[chemical symbol]] '''Ni''') is an [[element]]. It has an [[atomic number]] of 28 and an [[atomic mass]] of about 58.69amu. It has 28 [[proton]]s. It is a [[transition metal]]. ==Properties== ===Physical properties=== Nickel is a silver-white [[metal]]. It is easily polished (made shiny). It is [[magnetic]]. It is not magnetic when heated above {{convert|355|C|F}}. It is not soft like many other metals. It can be stretched into wires easily. It is not radioactive. ===Chemical properties=== Nickel is not a reactive metal. It dissolves slowly in acids. It does not rust like [[iron]]. It makes a thin coating of [[nickel(II) oxide]] which stops more corrosion. [[Aluminium]] does a similar thing. ===Chemical compounds=== [[File:Nickel(II)-chloride-hexahydrate-sample.jpg|thumb|right|alt=|Nickel(II) chloride]] [[File:Nickel(II)-sulfate-hexahydrate-sample.jpg|thumb|right|alt=|Nickel(II) sulfate]] Nickel is found in two [[oxidation state]]s: +2, nickel(II); and +3, nickel(III). Nickel(II) is more common. Nickel in its +2 oxidation state is green. [[Nickel(II) chloride]] is a common +2 oxidation state compound. Nickel(II) oxide is normally dark green, but sometimes it is gray. This is because some of the nickel is in the +3 oxidation state (nickel(III). Nickel(III) compounds are [[oxidizing agent]]s. They also are grayish. Nickel compounds can be green, blue, gray, or black. ;Nickel(II) compounds Nickel(II) compounds are not highly reactive. They are normally green or blue. They are toxic and irritate skin. Some of them are [[carcinogen]]s. *[[Nickel(II) carbonate]], green *[[Nickel(II) chloride]], greenish *[[Nickel(II) hydroxide]], light green *[[Nickel(II) nitrate]], greenish *[[Nickel(II) oxide]], gray or light green *[[Nickel(II) sulfate]], blue-green ;Nickel(III) compounds Nickel(III) compounds are black or gray. *[[Nickel(III) oxide]] ==Isotopes== The isotopes of nickel range