Protactinium

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Protactinium is a chemical element with the symbol Pa and atomic number 91.

 

General
Name, Symbol, Number protactinium, Pa, 91
Chemical series actinides
Group, Period, Block n/a, 7, f
Appearance bright, silvery metallic luster
Standard atomic weight 231.03588(2) g·mol-1
Electrons per shell 2, 8, 18, 32, 20, 9, 2
Physical properties
Phase solid
Density (near r.t.) 15.37 g·cm−3
Melting point 1841K
(1568°C, 2854°F)
Boiling point  ? 4300K
(? 4027°C, ?°F)
Heat of fusion 12.34 kJ·mol-1
Heat of vaporization 481 kJ·mol-1
Atomic properties
Crystal structure orthorhombic
Oxidation states 2, 3, 4, 5
(weakly basic oxide)
Electronegativity 1.5 (Pauling scale)
Ionization energies 1st: 568 kJ/mol
Atomic radius 180 pm
Miscellaneous
Magnetic ordering no data
Electrical resistivity (0 °C) 177 nΩ·m
Thermal conductivity (300K) 47 W·m-1·K-1
CAS registry number 7440-13-3

 

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