Changes: Actinium

Revision as of 00:36, 11 July 2017

Actinium is a radioactive chemical element with symbol Ac (not to be confused with the abbreviation for an acetyl group) and atomic number 89, which was discovered in 1899. It was the first non-primordial radioactive element to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902. Actinium gave the name to the actinides, a group of 15 similar elements between actinium and lawrencium in the periodic table.

A soft, silvery-white radioactive metal, actinium reacts rapidly with oxygen and moisture in air forming a white coating of actinium oxide that prevents further oxidation. As with most lanthanides and actinides, actinium assumes oxidation state +3 in nearly all its chemical compounds. Actinium is found only in traces in uranium and thorium ores as the isotope ²²⁷Ac, which decays with a half-life of 21.772 years, predominantly emitting beta and sometimes alpha particles, and ²²⁸Ac, which is beta active with a half-life of 6.15 hours. One tonne of natural uranium in ore contains about 0.2 milligrams of actinium-227, and one tonne of natural thorium contains about 5 nanograms of actinium-228. The close similarity of physical and chemical properties of actinium and lanthanum makes separation of actinium from the ore impractical. Instead, the element is prepared, in mg amounts, by the neutron irradiation of ²²⁶Ra in a nuclear reactor. Owing to its scarcity, high price and radioactivity, actinium has no significant industrial use. Its current applications include a neutron source and an agent for radiation therapy targeting cancer cells in the body.

@@ Line 1: / Line 1: @@
-'''Actinium''' is a radioactive chemical element with symbol '''Ac''' (not to be confused with the abbreviation for an acetyl group) and atomic number 89, which was discovered in 1899. It was the first non-primordial [[radioactive]] [[element]] to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902. Actinium gave the name to the [[actinide series]], a group of 15 similar elements between actinium and lawrencium in the periodic table.
+'''Actinium''' is a radioactive chemical element with symbol '''Ac''' (not to be confused with the abbreviation for an acetyl group) and atomic number 89, which was discovered in 1899. It was the first non-primordial [[radioactive]] [[element]] to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902. Actinium gave the name to the [[actinide|actinides]], a group of 15 similar elements between actinium and lawrencium in the periodic table.
 A soft, silvery-white radioactive
 <nowiki> </nowiki>metal, actinium reacts rapidly with oxygen and moisture in air forming a
+<nowiki> </nowiki>white coating of actinium oxide that prevents further oxidation. As with most [[lanthanide|lanthanides]] and [[actinide|actinides]], actinium assumes oxidation state +3 in nearly all its chemical compounds. Actinium is found only in traces in uranium and thorium ores as the isotope <sup>227</sup>Ac, which decays with a half-life of 21.772 years, predominantly emitting beta and sometimes alpha particles, and <sup>228</sup>Ac, which is beta active with a half-life of 6.15 hours. One tonne of natural uranium
-<nowiki> </nowiki>white coating of actinium oxide that prevents further oxidation. As
-with most [[lanthanides]] and [[actinides]], actinium assumes oxidation state +3 in nearly all its chemical compounds. Actinium is found only in traces in uranium and thorium ores as the isotope <sup>227</sup>Ac, which decays with a half-life of 21.772 years, predominantly emitting beta and sometimes alpha particles, and <sup>228</sup>Ac, which is beta active with a half-life of 6.15 hours. One tonne of natural uranium
 <nowiki> </nowiki>in ore contains about 0.2 milligrams of actinium-227, and one tonne of
 natural thorium contains about 5 nanograms of actinium-228. The close
 similarity of physical and chemical properties of actinium and lanthanum
 <nowiki> </nowiki>makes separation of actinium from the ore impractical. Instead, the
-element is prepared, in milligram amounts, by the neutron irradiation of
+element is prepared, in mg amounts, by the neutron irradiation of<nowiki> </nowiki><sup>226</sup>Ra in a nuclear reactor.<nowiki> </nowiki>Owing to its scarcity, high price and radioactivity, [[actinium]] has no
-<nowiki> </nowiki><sup>226</sup>Ra in a nuclear reactor.
-<nowiki> </nowiki>Owing to its scarcity, high price and radioactivity, actinium has no
 significant industrial use. Its current applications include a neutron
 source and an agent for radiation therapy targeting cancer cells in the body.