Template:Infobox actinium

Actinium,  ₈₉Ac

General properties
Name, symbol	actinium, Ac
Appearance	silvery-white, glowing with an eerie blue light; sometimes with a golden cast
Pronunciation	/ækˈtɪniəm/ ak-TIN-nee-əm
Actinium in the periodic table
La ↑ Ac ↓ (Uqu) radium ← actinium → thorium
Atomic number (Z)	89
Group, block	group n/a, f-block
Period	period 7
Element category	actinide, sometimes considered a transition metal
Standard atomic weight (Ar)	(227)
Electron configuration	[Rn] 6d1 7s2
per shell	2, 8, 18, 32, 18, 9, 2
Physical properties
Phase	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
Heat of vaporization	400 kJ/mol
Molar heat capacity	27.2 J/(mol·K)
Atomic properties
Oxidation states	3, 2 ​(a neutral oxide)
Electronegativity	Pauling scale: 1.1
Ionization energies	1st: 499 kJ/mol 2nd: 1170 kJ/mol
Covalent radius	215 pm
Miscellanea
Crystal structure	​face-centered cubic (fcc)
Thermal conductivity	12 W/(m·K)
CAS Number	7440-34-8
History
Discovery and first isolation	Friedrich Oskar Giesel (1902)
Most stable isotopes of actinium
iso NA half-life DM DE (MeV) DP 225Ac trace 10 d α 5.935 221Fr 226Ac syn 29.37 h β− 1.117 226Th ε 0.640 226Ra α 5.536 222Fr 227Ac trace 21.772 y β− 0.045 227Th α 5.042 223Fr

References

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