91 · Pa
Protactinium
The short-lived isotope is identified in 1913. Isotope 231 is isolated in 1917, in parallel, by Hahn and Meitner and by Soddy and Cranston.
Identity
- Atomic number
- 91
- Symbol
- Pa
- Canonical name
- Protactinium
- Category
- actinide
- Group
- unassigned
- Period
- 7
- Block
- f
Series set apart from the main table. Whether group 3 is lanthanum or lutetium (actinium or lawrencium) is still discussed, so the group is left empty.
Properties
These quantities come from the Periodic Table JSON compilation. They have not yet been checked, one by one, against CIAAW atomic weights or NIST measurements. A value marked estimated is not a measurement.
- Atomic mass
- 231.035882 u
- Electron configuration
- [Rn] 5f2 6d1 7s2
- Electrons per shell
- 2, 8, 18, 32, 20, 9, 2
- Standard state
- solid
- Density
- 15.37 g/cm³
- Melting point
- 1,841 K
- Boiling point
- 4,300 K
- Electronegativity
- 1.5 Pauling
- First ionization energy
- 568 kJ/mol
- Electron affinity
- 53.03 kJ/mol
History
Brevium
Identification · confirmed · 1913
Fajans and Göhring identify the short-lived isotope 234Pa. They do not isolate the long-lived isotope 231Pa.
Protactinium-231
Isolation · jointly credited · 1917
Hahn and Meitner isolate protactinium-231.
Parallel work
Isolation · jointly credited · 1917
Soddy and Cranston obtain the same isotope independently.
Etymology
- Theme
- property
- Language
- grec
- Root
- protos
- Meaning
- parent of actinium
Scientists
Places and institutions
- Berlin — historical setting : Prussia, then Germany — present country : Germany
Sources
- IUPAC, Periodic Table of the Elements
- Bowserinator, Periodic Table JSON. Compilation secondaire d’où viennent les grandeurs physiques importées (masse, densité, températures, énergies). Elles ne sont pas revérifiées une à une auprès du NIST ou de la CIAAW.
- John Emsley, Nature’s Building Blocks: An A–Z Guide to the Elements