History
(Gr. aktis, aktinos, beam or ray). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals.[1]
Properties
| General |
|---|
| Name : actinium |
| Symbol : Ac |
| Atomic Number : 89 |
| Chemical Series : Actinides |
| Block, Period : -, 7 |
| Appearance : silvery white |
| Atomic Properties |
| Atomic Weight : 227 |
| Covalent Radius (pm) : n/a |
| Physical Properties |
| Matter : solid (radioactive) |
| Density (kg/m3) : 10070 |
| Hardness : n/a |
| Melting Point (K) : 1323 |
| Boiling Point (K) : 3473 |
| Evaporation Heat (kJ/mol) : n/a |
| Fusion Heat (kJ/mol) : 62 |
| Specific Heat (J/(kg*K) ) : n/a |
| Miscellaneous |
| Electrical Conductivity (106/m ohm) : n/a |
| Thermal Conductivity (W/(m*K) ) : 12 |
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. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300-degrees C. 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.[1]
Notes
[1] From Los Alamos National Laboratory's Chemistry Division Website
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