Stable isotope Protactinium (Pa)

Isotope Atomic Mass Half-life Mode of Decay Nuclear Spin Nuclear Magnetic Moment
Pa-228 228.03100 22 hours EC to Th-228; α to Ac-224 3 3.5
Pa-229 229.03209 1.50 days EC to Th-229; α to Ac-225 5/2 No data available
Pa-230 230.03453 17.04 days EC to Th-230; α to Ac-226; β- to U-230 2 2.0
Pa-231 231.035880 32,500 years α to Ac-226; SF 3/2 2.01
Pa-232 232.03858 1.31 days EC to Th-232; β- to U-232 2 No data available
Pa-233 233.04024 27.00 days β- to U-233 3/2 4.0
Pa-234 234.04330 6.69 hours β- to U-234 4 No data available

Properties of Protactinium

Name Protactinium
Symbol Pa
Atomic number 91
Atomic weight 231.03588
Standard state Solid at 298 ºK
CAS Registry ID 7440-13-3
Group in periodic table N/A
Group name Actinoid
Period in periodic table 7 (Actinoid)
Block in periodic table f-block
Color Silvery metallic
Classification Metallic
Melting point 1568 °C
Boiling point 4000 °C
Thermal conductivity 47 (estimate) W/(m·K)
Electrical resistivity 18 x 10-8 Ω·m
Electronegativity 1.5
Heat of vaporization 470 kJ·mol-1
Heat of fusion 15 kJ·mol-1
Density of solid 15.370 g/cm3
Electron configuration [Rn]5f26d17s2
Atomic radius 1.63 Å (coordination number 12)
Oxidation states +4, +5