Electronic data		Thermal data		Steric data
Shells: 2,8,18,32,20,9,2 Orbitals: [Rn] 5f2 6d1 7s2 Electronegativity: 1.1, -- 1. Ionization potential: 5.89 eV 2. Ionization potential: -- eV 3. Ionization potential: -- eV Oxidation states: 5,4 Electrical conductivity: 0.0529 10^6		Melting point: 1600 °C Boiling point: -- °C Specific heat: 0.12 J/gK Heat of fusion: 12.30 kJ/mol Heat of vaporization: -- kJ/mol Thermal conductivity: 0.47 W/cmK		Atomic radius: -- Å Ionic radius: -- Å () Covalent radius: -- Å Atomic volume: 15.0 cm³/mol Density (293 K): 15.4 g/cm³ Crystal structure: Orthorhombic

Nuclide	Abundance [%]	Mass	Spin	Halflife	Decay mode	Decay tree
230Pa	0	230	2	17.4d	EC,-,	View
231Pa	0	231.036	3/2	3.28E04y		View
233Pa	0	233	3/2	27.0d	-	View
234Pa	0	234	4	6.69h	-	View
234Pam	0	234	0	1.17m	-,IT	View

Legend

Name origin:	Greek: proto and actinium (parent of actinium); it forms actinium when it radioactively decays.
Description:	Very rare, silvery-white, extremely radioactive metal.
Discovered by:	Fredrich Soddy, John Cranston, Otto Hahn, Lise Meitner
Year:	1917
Place:	England/France
Sources:	Does not occur in nature. Found among fission products of uranium, thorium, and plutonium.
Use(s):	It has no significant commercial applications.