temporary actinium
Material Overview
Actinium was discovered in 1899 by André-Louis Debierne. Its name derives from the Greek word aktinos, meaning "ray."
Actinium is a silvery metal with a cubic crystal form. It behaves like lanthanum, forming mostly the trivalent salts of the metal. It is strongly electropositive, the first ionization potential being 5.17 eV. It reacts with HCl, forming AcCl3, and also reacts with organic acids, forming their corresponding salts. Combustion in air can produce oxide and nitride. It is also susceptible to react with CO2, forming carbonate. It is used in nuclear reactors as a source of neutrons. Exposure to its radiation can cause cancer.
| Name | Actinium |
| Symbol | Ac |
| Atomic number | 89 |
| Atomic weight | 227 |
| Standard state | Solid at 298 ºK |
| CAS Registry ID | 7440-34-8 |
| Group in periodic table | N/A |
| Group name | Actinoids |
| Period in periodic table | 7 (Actinoid) |
| Block in periodic table | f-block |
| Color | Silvery |
| Classification | Metallic |
| Melting point | 1050 ºC |
| Boiling point | 3300 °C |
| Vaporization point | 3198 ºC |
| Thermal conductivity | 12 (estimate) W m-1 K-1 |
| Electronegativity | 1.1 |
| Heat of vaporization | 400 kJ mol-1 |
| Heat of fusion | 14 kJ mol-1 |
| Density of solid | 10070 kg/m-3 |
| Electronic configuration | [Rn]6d17s2 |
| Oxidation state | +3 |
Isotopes of Actinium
| Isotope | Mass | Half-life | Mode of Decay | Nuclear Spin | Nuclear Magnetic Moment |
| Ac-224 | 224.021708 | 2.7 hours | β- to Th-224; α to Fr-220; EC to Ra-224 | 0 | |
| Ac-225 | 225.02322 | 10.0 days | α to Fr-221 | 3/2 | |
| Ac-226 | 226.026089 | 1.224 days | β- to Th-226; α to Fr-222; EC to Ra-226 | 1 | |
| Ac-227 | 227.027750 | 21.77 years | β- to Th-228; α to Fr-224 | 3/2 | 1.1 |
| Ac-228 | 228.031104 | 6.15 hours | β- to Th-229 | 3 | |
| Ac-229 | 229.03293 | 1.04 hours | 3/2 |
