Protactinium

Metal

Symbol: Pa
Atomic number: 91
Atomic mass: 231.03588
Group: Actinide
CAS-number: 7440-13-3

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Electronic 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

Thermal data

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

Steric data

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

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.

Protactinium

Physical data

Electronic data

Thermal data

Steric data

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