91
Pa
Protactinium
Actinide period 7 f-block discovered: 1913
As a chemical element
Properties of the atom — they do not depend on what substance it is part of.
- Atomic number
- 91
- Atomic mass
- 231.03588 a.m.u.
- Electron configuration
- [Rn]7s2 5f2 6d1
- Electronegativity
- 1.5 on the Pauling scale
- Atomic radius
- 243 pm
- Ionization energy
- 5.89 eV
- Oxidation states
- +5, +4
As a simple substance
Properties of the substance these atoms form under ordinary conditions.
- State at 25 °C
- Solid
- Melting point
- 1845 K (1 571,85 °C)
- Density
- 15.37 g/cm³