Editing Californium (section)

=== Chemical properties and compounds ===
{{Further|Californium compounds}}
{| class="wikitable"
|+ Representative californium compounds{{sfn|Jakubke|1994|p=166}}{{efn|Other +3 oxidation states include the sulfide and [[metallocene]].{{sfn|Cotton|Wilkinson|Murillo|Bochmann|1999|p=1163}}}}
! state !! compound !! formula !! color !!
|-
| +2 || [[californium(II) bromide]] || CfBr{{sub|2}} || yellow || style="background:#FFDA5C;" |
|-
| +2 || [[californium(II) iodide]] || CfI{{sub|2}} || dark violet || style="background:#702A97;" |
|-
| +3 || [[californium(III) oxide]] || Cf{{sub|2}}O{{sub|3}} || yellow-green || style="background:#B4E532;" |
|-
| +3 || [[californium(III) fluoride]] || CfF{{sub|3}} || bright green || style="background:#59FF00;" |
|-
| +3 || [[californium(III) chloride]] || CfCl{{sub|3}} || emerald green || style="background:#26B645;" |
|-
| +3 || [[californium(III) bromide]] || CfBr{{sub|3}} || yellowish green || style="background:#81C340;" |
|-
| +3 || [[californium(III) iodide]] || CfI{{sub|3}} || lemon yellow || style="background:#FFE826;" |
|-
| +3
|[[californium(III) polyborate]]
|Cf[B{{sub|6}}O{{sub|8}}(OH){{sub|5}}]
|pale green || style="background:#96CD91;" |
|-
| +4 || [[californium(IV) oxide]] || CfO{{sub|2}} || black brown || style="background:#3D3016;" |
|-
| +4 || [[californium(IV) fluoride]] || CfF{{sub|4}} || green || style="background:#2B9E22;" |
|}
Californium exhibits oxidation states of 4, 3, or 2. It typically forms eight or nine bonds to surrounding atoms or ions. Its chemical properties are predicted to be similar to other primarily 3+ valence actinide elements{{sfn|Seaborg|2004}} and the element [[dysprosium]], which is the lanthanide above californium in the periodic table.{{sfn|CRC|2006|p=4.8}} Compounds in the +4 oxidation state are strong [[oxidizing agent]]s and those in the +2 state are strong [[reducing agent]]s.{{sfn|Jakubke|1994|p=166}}

The element slowly tarnishes in air at room temperature, with the rate increasing when moisture is added.{{sfn|O'Neil|2006|p=276}} Californium reacts when heated with [[hydrogen]], [[nitrogen]], or a [[chalcogen]] (oxygen family element); reactions with dry hydrogen and aqueous [[mineral acid]]s are rapid.{{sfn|O'Neil|2006|p=276}} <!-- EXPLAIN Only californium-249 is suitable for chemical study.<ref name="Emeleus">{{cite book|last=Emeleus|first=H. J.|title=Advances in Inorganic Chemistry|page=33|year=1987|publisher=Academic Press | isbn = 978-0-12-023631-2 }}</ref> /EXPLAIN -->

Californium is only [[aqueous solution|water-soluble]] as the californium(III) [[cation]]. Attempts to [[redox|reduce or oxidize]] the +3 ion in solution have failed.{{sfn|CRC|2006|p=4.8}} The element forms a water-soluble [[chloride]], [[nitrate]], [[perchlorate]], and [[sulfate]] and is precipitated as a [[fluoride]], [[oxalate]], or [[hydroxide]].{{sfn|Seaborg|2004}} Californium is the heaviest actinide to exhibit covalent properties, as is observed in the californium borate.<ref>{{Cite journal|title = Unusual structure, bonding and properties in a californium borate|journal = Nature Chemistry|date = May 1, 2014|issn = 1755-4330|pages = 387–392|volume = 6|issue = 5|doi = 10.1038/nchem.1896|pmid = 24755589|language = en|first1 = Matthew J.|last1 = Polinski|first2 = Edward B. Garner|last2 = Iii|first3 = Rémi|last3 = Maurice|first4 = Nora|last4 = Planas|first5 = Jared T.|last5 = Stritzinger|first6 = T. Gannon|last6 = Parker|first7 = Justin N.|last7 = Cross|first8 = Thomas D.|last8 = Green|first9 = Evgeny V.|last9 = Alekseev|url = http://hal.in2p3.fr/in2p3-00966875|bibcode = 2014NatCh...6..387P|citeseerx = 10.1.1.646.749| s2cid=104331283 }}</ref>