89 Ac 227
Actinium
Actinide
Actinium (Ac) is a chemical element with atomic number 89, classified as a actinide. At room temperature it is a solid. It was discovered in 1899 by André-Louis Debierne.
Properties
- Atomic number
- 89
- Atomic mass
- 227 u
- Category
- Actinide
- Group
- 3
- Period
- 7
- Block
- f-block
- Electron configuration
- [Rn] 6d¹ 7s²
- Phase at STP
- Solid
- Density
- 10.07 g/cm³
- Melting point
- 1323 K (1049.8 °C)
- Boiling point
- 3471 K (3197.8 °C)
- Electronegativity
- 1.1
- Atomic radius
- 260 pm
- Ionization energy
- 5.17 eV
- Discovery
- 1899 · André-Louis Debierne
Common uses
Cancer treatment, neutron sources, research
Did you know?
First of the actinides and glows blue in the dark.
Experiment with the elements
Actinium doesn't form any compounds in our lab yet, but the periodic table sandbox lets you combine dozens of other real elements into real compounds — water, table salt, ammonia and many more — with their true chemical formulas.