89Ac227.02775
Actinium
Actinide
Solid at STP
Period 7Block FDiscovered 1899
[Rn]7s2 6d1
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.
📖 Read more on Wikipedia →Atomic Properties
| Atomic Number | 89 |
| Atomic Mass | 227.02775 u |
| Electron Configuration | [Rn]7s2 6d1 |
| Oxidation States | +3 |
| Electronegativity | 1.1 (Pauling) |
| Atomic Radius | 260 pm |
| Ionization Energy | 5.17 eV |
| Block | F |
Physical Properties
| Standard State | Solid |
| Melting Point | 1324 K (1050.8 °C) |
| Boiling Point | 3471 K (3197.8 °C) |
| Density | 10.07 g/cm³ |
| Molar Heat | 27.2 J/(mol·K) |
| CPK Color | #70ABFA |
Classification
| Category | Actinide |
| Group Block | Actinide |
| Period | 7 |
| Block | F |
Discovery
| Year Discovered | 1899 |
| Discovered By | Friedrich Oskar Giesel |
| Electron Shells | 2, 8, 18, 32, 18, 9, 2 |