| Actinium - Ac
CAS: 7440-34-8 Description: Silvery-white radioactive metal Classification: Actinide Date of Discovery: 1899 Discoverer: Andre Debierne Name Origin: Greek aktinos, "beam or ray" |
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Atomic Number: 89
Number of Neutrons: 138 Atomic Mass: (227) amu Melting Point: 1051 °C Boiling Point: 3200 ± 300 °C (est.) Density (293 K): 10.07 g/cm3 (calc.) Atomic volume: 22.54 cm3/mol Electrical resistivity: Thermal conductivity: 0.12 W/cmK Enthalpy of atomization: 301 kJ/mol (est) Enthalpy of vaporization: Enthalpy of fusion: Specific heat capacity: 0.120 J/g/K |
Energy levels: 2-8-18-32-18-9-2
Electron configuration: [Rn]6d17s2 Crystal Structure: Cubic surface centered Atomic radius: Covalent radius: Oxidation States: +3 Electronegativity, Pauling: 1.1 Electron affinity: First ionization energy: 5.17 eV 2nd ionization energy: 12.126 eV 3rd ionization energy: Polarizability: 32.1 10-24cm3 |
| Isotope | Natural Abundance | Atomic Mass | Half-life | Decay Mode | Spin |
| 207Ac |  0.02 s |
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| 208mAc | 25 ms |
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| 208Ac | 0.1 s |
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| 209Ac | 209.0096 | 0.09 s |
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| 210Ac | 210.0093 | 0.4 s | |
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| 211Ac | 211.0076 | 0.3 s | |
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| 212Ac | 212.0078 | 0.9 s | |
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| 213Ac | 213.0066 | 0.8 s | |
(9/2-) | |
| 214Ac | 214.0069 | 8.2 s | |
(5+) | |
| 215Ac | 215.0065 | 0.17 s | |
(9/2-) | |
| 216mAc | 0.33 ms | |
(9-) | ||
| 216Ac | 216.00871 | 0.3 ms |
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(1) | |
| 217mAc | 0.7 µs | |
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| 217Ac | 217.00933 | 0.07 µs | |
9/2- | |
| 218Ac | 218.01162 | 1.1 µs | |
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| 219Ac | 219.01241 | 0.012 ms | |
(9/2-) | |
| 220Ac | 220.0148 | 26 ms | |
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| 221Ac | 221.01558 | 52 ms | |
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| 222mAc | 63 s | ; EC; IT |
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| 222Ac | 222.01782 | 5 s | |
1- | |
| 223Ac | 223.01913 | 2.1 m | ; EC |
(5/2-) | |
| 224Ac | 224.021708 | 2.7 h | EC; |
0- | |
| 225Ac | 225.02322 | 10.0 d | |
3/2 | |
| 226Ac | 226.026089 | 1.224 d | EC;  -; |
(1-) | |
| 227Ac | 227.027747 | 21.77 y | -; |
(3/2-) | |
| 228Ac | 228.031014 | 6.15 h | - |
(3+) | |
| 229Ac | 229.03293 | 1.04 h | - |
(3/2+) | |
| 230Ac | 230.0360 | 2.03 m | - |
1+ | |
| 231Ac | 231.0386 | 7.5 m | - |
(1/2+) | |
| 232Ac | 232.0420 | 2.0 m | - |
(2-) | |
| 233Ac | 2.4 m | - |
(1/2+) | ||
| 234Ac | 40 s | - |
(1+) | ||
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Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Thirty-two isotopes and isomers are now recognized. All are radioactive. Actinium-227, a decay product of uranium-235 is an alpha and beta emitter with a 2l.77-year half- life. Its principal decay products are thorium-227 (18.72-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared
by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300 °C. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.77-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons.
Actinium Decay Series (from 2U) 
LINKS: Actinium Decay Row Photon Interaction Coefficients of Actinium Return
Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998. |
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