Element 89
Actinium (Ac)
Actinium (Ac) is element 89 of the periodic table, a actinide in period 7 (f-block) with an atomic mass of 227 and is a solid at standard conditions.
At a glance
- Atomic number
- 89
- Symbol
- Ac
- Atomic mass
- 227 u
- Category
- Actinides
- Period
- 7
- Block
- f-block
- Phase at STP
- solid
Electron structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 6d1 7s2
- Shorthand configuration
- [Rn] 6d1 7s2
- Electrons per shell
- 2, 8, 18, 32, 18, 9, 2
- Oxidation states
- +2, +3
Physical properties
- Melting point
- 1323 K
- Boiling point
- 3471 K
- Density
- 10.07 g/cm3
- Phase
- solid
Atomic properties
- Electronegativity (Pauling)
- 1.1
- Atomic radius
- 195 pm
- Covalent radius
- 215 pm
- First ionization energy
- 499 kJ/mol
- Electron affinity
- 33 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| Ac-227 | 227.02775 | — | Half-life 21.8 years |
Common uses
- Neutron source
- Cancer treatment research
- Thermoelectric generators
Discovery
- Year
- 1899
- Discovered by
- André-Louis Debierne
- Country
- France