Actinium

89

Ac

(227)
  • Name: Actinium
  • Symbol: Ac
  • Atomic number: 89
  • Atomic weight: (227)
  • CAS Registry ID: 7440-34-8
  • Group name: Actinoid
  • Period number: 7
  • Block: f-block
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Description

Actinium is an element classified as an actinide. It is silvery solid in its natural state, is highly radioactive, and will glow a light blue color in the dark. Actinium has an atomic weight of 227, a melting point of 1922 ° F, and a boiling point of 5788 °F. Actinium is so radioactive and dangerous that it has no commercial uses. It is used as a neutron source for some chemical reactions and as a component in radio-immunotherapy for Targeted Alpha Therapy.

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Isolation

Actinium is not normally isolated as it is so dangerous. However, it can be synthesized, or isolated, on a very small scale for its uses listed above.

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The only place in nature where actinium is found is in trace amounts of uranium ores such as pitchblende. Pitchblende is a mineral which contains high amounts of uranium in addition to oxides of lead and rare earth elements; it is also known as uraninite. Actinium can be isolated from pitchblende, but this process is rarely carried out. In order to isolate the actinium from pitchblende, it must be first reduced to its fluoride form. After this is done, the fluoride of actinium is reduced with lithium vapor and heated to between 2012 - 2372 °F. This process will yield minute amounts of pure actinium. Small amounts of actinium can also be produced through the neutron irradiation on the radium isotope, number 226; this procedure is carried out in a nuclear reactor. Storage and handling of actinium is carried out with extreme caution due to its high toxicity and extreme radioactive traits.
General
Name Actinium
Symbol Ac
Number 89
Chemical series actinides
Group 3
Period 7
Block f
Appearance silvery
Standard atomic weight (227)  g·mol−1
Electron configuration [Rn] 6d1 7s2
Electrons per shell 2, 8, 18, 32, 18, 9, 2
Atomic properties
Crystal structure cubic face centered
Oxidation states 3 (neutral oxide)
Electronegativity 1.1 (scale Pauling)
Ionization energies 1st: 499 kJ/mol
(more) 2nd: 1170 kJ/mol
(more)
Atomic radius 195 pm
Atomic radius (calc.)
Covalent radius
Van der Waals radius
Physical properties
Phase solid
Density (near r.t.) 10  g·cm−3
Liquid density at m.p.
Melting point (circa) 1323 K (1050 °C, 1922 °F)
Boiling point 3471 K (3198 °C, 5788 °F)
Critical point
Heat of fusion 14  kJ·mol−1
Heat of vaporization 400  kJ·mol−1
Heat capacity (25 °C) 27.2  J·mol−1·K−1
Miscellaneous
Magnetic ordering
Electrical resistivity
Thermal conductivity (300 K) 12  W·m−1·K−1
Thermal expansion
Speed of sound (thin rod)
Young's modulus
Shear modulus
Bulk modulus
Poisson ratio
Mohs hardness
Vickers hardness
Brinell hardness
CAS registry number 7440-34-8

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