Discovery date : 1899
Discovered by: Andrew Debierne
Origin of the name: The name is derived from the Greek 'actinos', meaning a ray.
Allotropes :
~>ACTINIUM s a chemical element with symbol Ac and atomic number 89. Actinium gave the name to the actinide series, a group of 15 similar elements between actinium and lawrencium in the periodic table.
| FACT BOX | |||
| Group | Actinides | Melting point | 1050°C, 1922°F, 1323 K |
| Period | 7 | Boiling point | 3200°C, 5792°F, 3473 K |
| Block | d | Density (g cm−3) | 10 |
| Atomic number | 89 | Relative atomic mass | [227] |
| State at 20°C | Solid | Key isotopes | 227Ac |
| Electron configuration | [Rn] 6d17s2 | CAS number | 7440-34-8 |
| ChemSpider ID | 22404 | ChemSpider is a free chemical structure database | |
This element was discovered in 1899 by André Debierne at Paris. He extracted it from the uranium ore pitchblende (uranium oxide, U3O8) in which it occurs in trace amounts. In 1902, Friedrich Otto Giesel independently extracted it from the same mineral and, unaware it was already known, gave it the named emanium.
Actinium extracted from uranium ores is the isotope actinium-227 which has half-life of 21.7 years. It occurs naturally as one of the sequence of isotopes that originate with the radioactive decay of uranium-235. A tonne of pitchblende contains around 150 mg of actinium.