SymbolPa
Latin nameProtaktinium
Atomic number91
Period7
Element categoryInner transition elements
Relative atomic mass231.0359
GroupV.B
Electronegativity
1.5
Oxidation numbers
4, 5
Electron configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p6 5f2 6d1 7s2
Density [g/cm3]
15.37
State
Solid
Melting point [°C]
1550
Boiling point [°C]
4225
Thermal conductivity [W m-1K-1]
47
Discovery
1917
1.st ionization energy [eV]
5.89
Stable isotopes
0
Unstable isotopes
13