Actinium

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Actinium is a chemical element with the symbol Ac and atomic number 89. Actinium is a silvery, radioactive, metallic element. Due to its intense radioactivity, actinium glows in the dark with a pale blue light. The chemical behavior of actinium is similar to that of the rare earth lanthanum.

 

General
Name, Symbol, Number actinium, Ac, 89
Chemical series actinides
Group, Period, Block 3, 7, f
Appearance silvery
Standard atomic weight (227) g·mol-1
Electrons per shell 2, 8, 18, 32, 18, 9, 2
Physical properties
Phase solid
Density (near r.t.) 10 g·cm−3
Melting point (circa) 1323K
(1050°C, 1922°F)
Boiling point 3471K
(3198°C, 5788°F)
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
Atomic properties
Crystal structure cubic face centered
Oxidation states 3
(neutral oxide)
Electronegativity 1.1 (Pauling scale)
Ionization energies 1st: 499 kJ/mol
2nd: 1170 kJ/mol
Atomic radius 195 pm
Miscellaneous
Magnetic ordering no data
Thermal conductivity (300K) 12 W·m-1·K-1
CAS registry number 7440-34-8

 

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