Actinium - 89Ac: the essentials
- Name: actinium
- Symbol: Ac
- Atomic number: 89
- Relative atomic mass (Ar): [ 227 ] (longest lived isotope)
- Standard state: solid at 298 K
- Appearance: silvery
- Classification: Metallic
- Group in periodic table:
- Group name: Actinoid
- Period in periodic table: 7 (actinoid)
- Block in periodic table: f
- Shell structure: 22.214.171.124.18.9.2
- CAS Registry: 7440-34-8
Actinium atoms have 89 electrons and the shell structure is 126.96.36.199.18.9.2. The ground state electronic configuration of neutral actinium is [Rn].6d1.7s2 and the term symbol of actinium is 2D3/2.
Actinium is dangerously radioactive. The chemical behaviour of actinium is similar to that of the rare earths, particularly lanthanum. It is found naturally in uranium ores and actinium is 150 times more radioactive than radium.
This sample of uraninite contains some about 10-9 grammes of actinium at any one time. Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.
Actinium: physical properties
- Density of solid: 10070 kg m-3
- Molar volume: 22.55 cm3
- Thermal conductivity: 12 (estimate) W m‑1 K‑1
Actinium: heat properties
- Melting point: 1323 [1050 °C (1922 °F)] K
- Boiling point: 3573 [3300 °C (5972 °F)] K
- Enthalpy of fusion: 20.5 kJ mol-1
Actinium: atom sizes
- Atomic radius (empirical): 195 pm
- Molecular single bond covalent radius: 186 (coordination number 3) ppm
- van der Waals radius: 283 ppm
- Pauling electronegativity: 1.1 (Pauling units)
- Allred Rochow electronegativity: 1.00 (Pauling units)
- Mulliken-Jaffe electronegativity: (no data)
Actinium: orbital properties
- First ionisation energy: 519.11 kJ mol‑1
- Second ionisation energy: 1134 kJ mol‑1
- Third ionisation energy: 1682 kJ mol‑1
- Universe: (no data) ppb by weight
- Crustal rocks: (no data) ppb by weight
- Human: (no data) ppb by weight
Actinium: crystal structure
Actinium: biological data
- Human abundance by weight: (no data) ppb by weight
Actinium has no biological role.
Reactions of actinium as the element with air, water, halogens, acids, and bases where known.
Actinium: binary compounds
Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of actinium where known.
Actinium: compound properties
Bond strengths; lattice energies of actinium halides, hydrides, oxides (where known); and reduction potentials where known.
Actinium: historyActinium was discovered by Andre Debierne in 1899 at France. Origin of name: from the Greek word "aktinos" meaning "ray".
Isolation: coming soon!