{{Elementbox_header | number=89 | symbol=Ac | name=actinium | left=[[radium]] | right=[[thorium]] | above=[[lanthanum|La]] | below=[[Untriennium|Ute]] | color1=#ff99cc | color2=black }}
{{Elementbox_series | [[actinide]]s }}
{{Elementbox_groupperiodblock | group=3 | period=7 | block=f }}
{{Elementbox_appearance | silvery }}
{{Elementbox_atomicmass_gpm | [[1 E-25 kg|(227)]] }}
{{Elementbox_econfig | [[[radon|Rn]]] 6d¹ 7s² }}
{{Elementbox_epershell | 2, 8, 18, 32, 18, 9, 2 }}
{{Elementbox_section_physicalprop | color1=#ff99cc | color2=black }}
{{Elementbox_phase | [[solid]] }}
{{Elementbox_density_gpcm3nrt | 10 }}
{{Elementbox_meltingpoint | k=(circa) 1323 | c=1050 | f=1922 }}
{{Elementbox_boilingpoint | k=3471 | c=3198 | f=5788 }}
{{Elementbox_heatfusion_kjpmol | 14 }}
{{Elementbox_heatvaporiz_kjpmol | 400 }}
{{Elementbox_heatcapacity_jpmolkat25 | 27.2 }}
{{Elementbox_section_atomicprop | color1=#ff99cc | color2=black }}
{{Elementbox_crystalstruct | cubic face centered }}
{{Elementbox_oxistates | 3<br />(neutral oxide) }}
{{Elementbox_electroneg_pauling | 1.1 }}
{{Elementbox_ionizationenergies2 | 499 | 1170 }}
{{Elementbox_atomicradius_pm | [[1 E-10 m|195]] }}
{{Elementbox_section_miscellaneous | color1=#ff99cc | color2=black }}
{{Elementbox_magnetic | no data }}
{{Elementbox_thermalcond_wpmkat300k | 12 }}
{{Elementbox_cas_number | 7440-34-8 }}
{{Elementbox_isotopes_begin | color1=#ff99cc | color2=black }}
{{Elementbox_isotopes_decay | mn=225 | sym=Ac
| na=[[synthetic radioisotope|syn]] | hl=[[1 E s|10 days]]
| dm=[[alpha decay|α]] | de=5.935 | pn=221 | ps=[[francium|Fr]] }}
{{Elementbox_isotopes_decay3 | mn=226 | sym=Ac
| na=[[synthetic radioisotope|syn]] | hl=[[1 E s|29.37 hours]]
| dm1=[[beta emission|β^-]] | de1=1.117 | pn1=226 | ps1=[[thorium|Th]]
| dm2=[[electron capture|ε]] | de2=0.640 | pn2=226 | ps2=[[radium|Ra]]
| dm3=[[alpha decay|α]] | de3=5.536 | pn3=222 | ps3=[[francium|Fr]] }}
{{Elementbox_isotopes_decay2 | mn=227 | sym=Ac
| na=100% | hl=[[1 E s|21.773 years]]
| dm1=[[beta emission|β^-]] | de1=0.045 | pn1=227 | ps1=[[thorium|Th]]
| dm2=[[alpha decay|α]] | de2=5.042 | pn2=223 | ps2=[[francium|Fr]] }}
{{Elementbox_isotopes_end}}
{{Elementbox_footer | color1=#ff99cc | color2=black }}

'''Actinium''' ({{pronEng|ækˈtɪniəm}}) is a [[chemical element]] with the symbol '''Ac''' and [[atomic number]] 89.

==Notable characteristics==
Actinium is a silvery, [[radioactive]], metallic element. Due to its intense radioactivity, Actinium glows in the dark with a pale blue light. It is found only in traces in uranium ores as ²²⁷Ac, an [[alpha radiation|α]] and [[beta radiation|β emitter]] with a [[half-life]] of 21.773 years. One ton of [[uranium]] ore contains about a tenth of a gram of actinium.

==Applications==
It is about 150 times as radioactive as radium, making it valuable as a [[neutron source]]. Otherwise it has no significant industrial applications.

²²⁵Ac is used in medicine to produce ²¹³{{bismuth}} in a reusable generator or can be used alone as an agent for radio-immunotherapy for Targeted Alpha Therapy (TAT). ²²⁵Ac was first produced artificially by the ITU in Germany using a cyclotron and by Dr Graeme Melville at St George Hospital in Sydney using a linac in 2000.

==History==
Actinium was discovered in [[1899]] by [[André-Louis Debierne]], a French chemist, who separated it from [[uraninite|pitchblende]]. [[Friedrich Oskar Giesel]] independently discovered actinium in [[1902]] and called it "emanium" in 1904. Debierne's name was retained because it had seniority. The chemical behavior of actinium is similar to that of the rare earth [[lanthanum]].

The word actinium comes from the Greek ''aktis, aktinos'', meaning beam or ray.

==Occurrence==
Actinium is found in trace amounts in [[uranium ore]], but more commonly is made in milligram amounts by the neutron irradiation of ²²⁶{{radium}} in a nuclear reactor. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300ºC.

==Isotopes==
{{main|isotopes of actinium}}
Naturally occurring actinium is composed of 1 radioactive [[isotope]]; ²²⁷Ac. 36 [[radioisotope]]s have been characterized with the most stable being ²²⁷Ac with a [[half-life]] of 21.772 [[year|y]], ²²⁵Ac with a half-life of 10.0 [[day]]s, and ²²⁶Ac with a half-life of 29.37 [[hour|h]]. All of the remaining [[radioactive decay|radioactive]] isotopes have half-lifes that are less than 10 hours and the majority of these have half lifes that are less than 1 minute. The shortest-lived isotope of actinium is ²¹⁷Ac which decays through [[alpha decay]] and [[electron capture]]. It has a half-life of 69 [[nanoseconds|ns]]. Actinium also has 2 [[meta state]]s.

Purified ²²⁷Ac comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.773-year half-life.

The isotopes of actinium range in [[atomic weight]] from 206 [[atomic mass unit|u]] (²⁰⁶Ac) to 236 u (²³⁶Ac).

==Precautions==
²²⁷Ac is extremely radioactive, and in terms of its potential for radiation induced health effects, ²²⁷Ac is even more dangerous than [[plutonium]]. Ingesting even small amounts of ²²⁷Ac would be fatal.{{Fact|date=November 2007}}

==References==
*[http://periodic.lanl.gov/elements/89.html Los Alamos National Laboratory - Actinium]

==External links==
{{Commons|Actinium}}
{{wiktionary|actinium}}
*[http://www.webelements.com/webelements/elements/text/Ac/index.html WebElements.com - Actinium]
*[http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@na+@rel+actinium,+radioactive NLM Hazardous Substances Databank &ndash; Actinium, Radioactive]
[[Category:Chemical elements]]
[[Category:Actinides]]

[[af:Aktinium]]
[[ar:أكتينيوم]]
[[bn:অ্যাক্টিনিয়াম]]
[[be:Актыній]]
[[bs:Aktinijum]]
[[ca:Actini]]
[[cs:Aktinium]]
[[co:Attiniu]]
[[da:Actinium]]
[[de:Actinium]]
[[et:Aktiinium]]
[[el:Ακτίνιο]]
[[es:Actinio]]
[[eo:Aktinio]]
[[eu:Aktinio]]
[[fa:آکتینیوم]]
[[fr:Actinium]]
[[fur:Atini]]
[[gl:Actinio (elemento)]]
[[ko:악티늄]]
[[hy:Ակտինիում]]
[[hr:Aktinij]]
[[io:Aktiniumo]]
[[id:Aktinium]]
[[it:Attinio]]
[[he:אקטיניום]]
[[ht:Aktiniòm]]
[[la:Actinium]]
[[lv:Aktīnijs]]
[[lb:Actinium]]
[[lt:Aktinis]]
[[jbo:jinmrtaktini]]
[[hu:Aktínium]]
[[nl:Actinium]]
[[ja:アクチニウム]]
[[no:Actinium]]
[[nn:Actinium]]
[[oc:Actini]]
[[pl:Aktyn]]
[[pt:Actínio]]
[[ro:Actiniu]]
[[qu:Aktinyu]]
[[ru:Актиний]]
[[simple:Actinium]]
[[sk:Aktínium]]
[[sl:Aktinij]]
[[sr:Актинијум]]
[[sh:Aktinijum]]
[[fi:Aktinium]]
[[sv:Aktinium]]
[[th:แอกทิเนียม]]
[[tr:Aktinyum]]
[[uk:Актиній]]
[[zh-yue:錒]]
[[zh:锕]]