|
|
Atomic Number: |
89 |
Melting Point: | 1051 ºC | |
| Atomic Symbol: | Ac | Boiling Point: | 3159 ºC | ||
| Atomic Weight: | 227 amu | Density: | 10070
kg/m 3 |
||
| Atomic Radius: |
187.8 pm |
Oxidation States: | 3 | ||
| Covalent Radius: | -- | Electron Configuration: | [Rn]7s26d1 | ||
| van der Waals Radius: |
-- |
State of Matter: | solid |
(Gr. aktis, aktinos, beam or ray). Discovered by Andre Debierne in 1899 by separating it from pitchblende. It was later discovered independently by F. Giesel in 1902.
Properties
Actinium is a silvery radioactive metallic element. Actinium glows in the dark due to its intense radioactivity with an eerie blue light. In equilibrium with its decay products, it is a powerful source of alpha rays. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.6-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons.
Actinium occurs naturally in association with uranium minerals. It has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300-degrees C. Milligram amounts are commonly made by the neutron irradiation of 226-Ra in a nuclear reactor.
Actinium-225 is used in medicine to produce Bi-213 in a reusable generator or can be used alone as an agent for radio-immunotherapy.
Actinium-227, a decay product of uranium-235, is a beta emitter with a 21.6-year half-life. Its principal decay products are thorium-227 (18.5-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes.
This element has 27 radioisotopes with the most stable being 227-Ac with a half-life of 21.773 years, 225-Ac with a half-life of 10 days, and 226-Ac with a half-life of 29.37 hours. 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. This element also has 2 meta states.
Actinium-227 is extremely radioactive, and in terms of its potential for radiation induced health effects, actinium-227 is about as dangerous as plutonium. Ingesting even small amounts of actinium-227 would represent a serious health hazard.
