Template:Infobox actinium

Actinium,  ₈₉Ac

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General properties
Pronunciation	Template:Infobox element/pronunciation
Appearance	silvery-white, glowing with an eerie blue light; sometimes with a golden cast
Standard atomic weight (Ar, standard)	Template:Infobox element/standard atomic weight
Mass number	Template:Infobox element/symbol-to-most-stable-isotope (most stable isotope)
Actinium in the periodic table
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Atomic number (Z)	89
Group	Template:Infobox element/group
Period	period 7
Block	d-block
Element category	Template:Infobox element/category format, sometimes considered a transition metal
Electron configuration	[Rn] 6d1 7s2
Electrons per shell	2, 8, 18, 32, 18, 9, 2
Physical properties
Phase at STP	solid
Melting point	1500 K ​(1227 °C, ​2240 °F) (estimated)
Boiling point	3500±300 K ​(3200±300 °C, ​5800±500 °F) (extrapolated)
Density (near r.t.)	10 g/cm3
Heat of fusion	14 kJ/mol
[[Enthalpy of vaporization|Heat of Template:Engvar]]	400 kJ/mol
Molar heat capacity	27.2 J/(mol·K)
Atomic properties
Oxidation states	Template:Infobox element/symbol-to-oxidation-state
Electronegativity	Pauling scale: 1.1
[[Ionization energy|Template:Engvar energies]]	1st: 499 kJ/mol 2nd: 1170 kJ/mol 3rd: 1900 kJ/mol (more)
Covalent radius	215 pm
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Other properties
Crystal structure	​Template:Infobox element/crystal structure Template:Infobox element/crystal structure
Thermal conductivity	12 W/(m·K)
CAS Number	7440-34-8
History
Discovery and first isolation	Friedrich Oskar Giesel (1902)
Named by	André-Louis Debierne (1899)
Main isotopes of actinium
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