91 Pa
Actinide
Protactinium
Rare radioactive metal.
Properties of Protactinium
- Atomic number (Z)
- 91
- Symbol
- Pa
- Atomic mass
- 231.04 g/mol
- Category
- Actinide
- Group
- 3
- Period
- 7
- Electron configuration
- [Rn] 5f² 6d¹ 7s²
- Electronegativity (Pauling)
- 1.5
- Atomic radius
- 180 pm
- First ionization energy
- 568 kJ/mol
- Melting point
- 1841 K (1567.8 °C)
- Boiling point
- 4300 K (4026.8 °C)
- Density
- 15.37 g/cm³
- Phase at 25 °C
- Solid
- Discovered
- Discovered in 1913