What is Cobalt?
[[File:Cobalt-3.jpg|thumb|Sheet of cobalt metal]] '''Cobalt''' ([[chemical symbol]] '''Co''') is a [[chemical element]]. It has an [[atomic number]] of 27 and an [[atomic mass]] of about 59. It is a [[metal]].<ref>{{Cite web|date=|title=How many valence electrons does Cobalt (Co) have?|url=https://guide-scientific.com/valence-electrons/how-many-valence-electrons-does-cobalt-have/|access-date=|website=|language=}}</ref> ==Properties== [[File:Cobalt(II)-chloride-hexahydrate-sample.jpg|thumb|Cobalt(II) chloride with water]] [[File:Cobalt(II) chloride.jpg|right|thumb|Cobalt(II) chloride without water]] Cobalt is a [[transition metal]]. It is shiny and conducts electricity. It is [[magnet]]ic. It is a hard metal. It is moderately [[chemical reaction|reactive]]. [[Iron]] is more reactive and [[copper]] is less reactive. It dissolves slowly in [[acid]]s. This reaction makes [[hydrogen]] and a [[salt]] of cobalt. Cobalt is normally in its +2 [[oxidation state]] as an [[ion]]. Some [[chemical compound]]s contain cobalt ions in its +4 oxidation state. [[Cobalt(II) chloride]] is one of the most common cobalt compounds. Many cobalt compounds are blue or pink. One of them is black. ===Chemical compounds=== Cobalt comes in two [[oxidation state]]s, +2 and +3. Most soluble cobalt compounds are red. They can also be green, blue, brown, and black. ;Cobalt(II) compounds *[[Cobalt(II) chloride]], red solid, most common cobalt compound *[[Cobalt(II) fluoride]], used in dentistry, red solid *[[Cobalt(II) hydroxide]], red or green-blue solid *[[Cobalt(II) oxide]], black solid *[[Cobalt(II) sulfate]], reddish solid, used in pigments ;Mixed oxidation state *[[Cobalt(II,III) oxide]], black solid, oxidizing agent ;Cobalt(III) compounds *[[Cobalt(III) fluoride]], brown solid, strong oxidizing agent *[[Cobalt(III) oxide]], black solid ==Occurrence and preparation== Cobalt is too reactive to occur as a pure element in the earth. It is found in certain [[mineral]]s. It is found with copper and [[nickel]] deposits. Normally the three met