Protactinium · Pa Protactinium
is a natural rare radioactive element, mainly used in nuclear chemistry and geochemistry research.
- atomic number / Atomic number
- 91
- atomic weight / Atomic mass
- 231.03588 u
- Family/Group
- Actinium series (independent row)
- Period · Block / Period · Block
- 7 · f
- Category / Category
- Actinium series · Actinide
- State / State
- solid state
- Electron configuration
- [Rn]7s2 5f2 6d1
- Oxidation states / Oxidation states
- +5, +4
- Electronegativity / Electronegativity
- 1.5（Pauling）
- Density / Density
- 15.37 g/cm³
- Melting point / Melting point
- 1845 K
- Boiling point / Boiling point
- not included
- Atomic radius / Atomic radius
- 243 pm（van der Waals）
- First ionization energy
- 5.89 eV
- Discovery year / Discovery
- 1913
attribute description and data source
properties taken from PubChem periodic table snapshot (2026-10-04). Atomic weights may be reference values or representative isotope masses and cannot be considered exact constants for all samples; density, phase transition points, and phase states depend on temperature, pressure, and allotropes. The solidification of helium requires pressure. Some properties of radioactive and superheavy elements are predicted values, and missing items are marked as not included. Please check the original source and experimental conditions for precise calculations.