89Solid
Ac 227 Atomic mass · uActinides
Actinium
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.
Discovery 1899 (Friedrich Oskar Giesel)
K2L8M18N32O18P9Q2
Physical properties
Values for the element in its standard state.
- Density
- 10.07g/cm³
- Melting point
- 1,323K
- Boiling point
- 3,473K
- Atomic radius
- Not available
- Bonding type
- Metallic
- Molar heat
- 27.2J/(mol·K)
Inside the atom
Electron arrangement and the energy behind its behavior.
Full electron configuration
1s, 2 electrons; 2s, 2 electrons; 2p, 6 electrons; 3s, 2 electrons; 3p, 6 electrons; 3d, 10 electrons; 4s, 2 electrons; 4p, 6 electrons; 4d, 10 electrons; 5s, 2 electrons; 5p, 6 electrons; 4f, 14 electrons; 5d, 10 electrons; 6s, 2 electrons; 6p, 6 electrons; 6d, 1 electrons; 7s, 2 electrons;
[Rn] represents 86 core electrons. The full view shows them explicitly.
89 electrons Orbital order preserved from source
- Electronegativity
- 1.1Pauling scale
- First ionization energy
- 499kJ/mol
- Electron affinity
- Not available
- Van der Waals radius
- Not available
Ac ActiniumAtomic number 89
499kJ/mol
Atomic numberGaps indicate unavailable data
About actinium
- Appearance
- Not recorded
- Discovery
- 1899 (Friedrich Oskar Giesel)
- Data source
- Read the reference
A missing value means it is unavailable in this reference dataset. Values can vary with measurement method and conditions.