Actinium

Actinium (pronEng|ækˈtɪniəm) is a radioactive chemical element with the symbol Ac and atomic number 89, which was discovered in 1899, the earliest discovered of the radioactive elements.

Characteristics

Actinium is a silvery, radioactive, metallic element. Due to its intense radioactivity, actinium glows in the dark with a pale blue light. The chemical behavior of actinium is similar to that of the rare earth element lanthanum.

Actinium is found only in traces in uranium ores as ²²⁷Ac, an α and β emitter with a half-life of 21.773 years. One ton of uranium ore contains about a tenth of a gram of actinium. The actinium isotope ²²⁷Ac is a transient member of the actinium series decay chain, which begins with the parent isotope ²³⁵U (or ²³⁹Pu) and ends with the stable lead isotope ²⁰⁷Pb. Another actinium isotope (²²⁵Ac) is transiently present in the neptunium series decay chain, beginning with ²³⁷Np (or ²³³U) and ending with near-stable bismuth (²⁰⁹Bi).

Applications

It is about 150 times as radioactive as radium, making it valuable as a neutron source for energy. Otherwise it has no significant industrial applications.

²²⁵Ac is used in medicine to produce ²¹³bismuth 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 pitchblende as a substance being similar to titanium (1899) [cite journal
title = Sur un nouvelle matière radio-active
author = André-Louis Debierne
journal = Comptes rendus
volume = 129
issue =
pages = 593–595
year = 1899
url = http://gallica.bnf.fr/ark:/12148/bpt6k3085b/f593.table
doi = ] or similar to thorium (1890) [cite journal
title = Sur un nouvelle matière radio-actifl'actinium
author = André-Louis Debierne
journal = Comptes rendus
volume = 130
issue =
pages = 906–908
year = 1900
url = http://gallica.bnf.fr/ark:/12148/bpt6k3086n/f906.table
doi = ] . Friedrich Oskar Giesel independently discovered actinium in 1902 [cite journal
title = Ueber Radium und radioactive Stoffe
author = Friedrich Oskar Giesel
journal = Berichte der Deutschen Chemische Geselschaft
volume = 35
issue = 3
pages = 3608–3611
year = 1902
url =
doi = 10.1002/cber.190203503187 ] as a substance being similar to lanthanum and called it "emanium" in 1904 [cite journal
title = Ueber den Emanationskörper (Emanium)
author = Friedrich Oskar Giesel
journal = Berichte der Deutschen Chemische Geselschaft
volume = 37
issue = 2
pages = 1696–1699
year = 1904
url =
doi = 10.1002/cber.19040370280 ] . After a comparison of substances in 1904, Debierne's name was retained because it had seniority. [cite journal
title = Ueber Emanium
author = Friedrich Oskar Giesel
journal = Berichte der Deutschen Chemische Geselschaft
volume = 37
issue = 2
pages = 1696–1699
year = 1904
url =
doi = 10.1002/cber.19040370280 ] [cite journal
title = Ueber Emanium
author = Friedrich Oskar Giesel
journal = Berichte der Deutschen Chemische Geselschaft
volume = 38
issue = 1
pages = 775–778
year = 1905
url =
doi = 10.1002/cber.190503801130 ]

The history of the discovery stayed questionable and in publications from 1971 [cite journal
title = The Discovery of Actinium
author = H. W. Kirby
journal = Isis
volume = 62
issue = 3
pages = 290–308
year = 1971
url = http://www.jstor.org/stable/view/229943?seq=1
doi = ] and later in 2000 [cite journal
title = The centenary of a controversial discovery: actinium
author = J. P. Adloff
journal = Radiochim. Acta,
volume = 88
issue =
pages = 123
year = 2000
url =
doi = 10.1524/ract.2000.88.3-4.123 ] showed that the claims of André-Louis Debierne in 1904 conflict with the publications in 1899 and 1890.

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 ²²⁶radium in a nuclear reactor. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300°C.

Isotopes

Naturally occurring actinium is composed of 1 radioactive isotope; ²²⁷Ac. 36 radioisotopes have been characterized with the most stable being ²²⁷Ac with a half-life of 21.772 y, ²²⁵Ac with a half-life of 10.0 days, and ²²⁶Ac with a half-life of 29.37 h. All of the remaining 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 ns. Actinium also has 2 meta states.

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 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

Fictional Applications

Actinium compounds, along with advanced circuitry are used in a time travel device in

ee also

*Actinium series

References

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

External links

* [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 – Actinium, Radioactive]