91Solid
Pa 231.036 Atomic mass · uActinides
Protactinium
Protactinium is a chemical element with symbol Pa and atomic number 91. It is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds where protactinium is usually present in the oxidation state +5, but can also assume +4 and even +2 or +3 states.
Discovery 1913 (William Crookes)
K2L8M18N32O20P9Q2
Physical properties
Values for the element in its standard state.
- Density
- 15.37g/cm³
- Melting point
- 1,845K
- Boiling point
- 4,273K
- Atomic radius
- Not available
- Bonding type
- Metallic
- Molar heat
- Not available
Inside the atom
Electron arrangement and the energy behind its behavior.
Full electron configuration
1s, 2 electrons; 2s, 2 electrons; 2p, 6 electrons; 3s, 2 electrons; 3p, 6 electrons; 3d, 10 electrons; 4s, 2 electrons; 4p, 6 electrons; 4d, 10 electrons; 5s, 2 electrons; 5p, 6 electrons; 4f, 14 electrons; 5d, 10 electrons; 6s, 2 electrons; 6p, 6 electrons; 5f, 2 electrons; 6d, 1 electrons; 7s, 2 electrons;
[Rn] represents 86 core electrons. The full view shows them explicitly.
91 electrons Orbital order preserved from source
- Electronegativity
- 1.5Pauling scale
- First ionization energy
- 568kJ/mol
- Electron affinity
- Not available
- Van der Waals radius
- Not available
Pa ProtactiniumAtomic number 91
568kJ/mol
Atomic numberGaps indicate unavailable data
About protactinium
- Appearance
- Bright, silvery metallic luster
- Discovery
- 1913 (William Crookes)
- Data source
- Read the reference
A missing value means it is unavailable in this reference dataset. Values can vary with measurement method and conditions.