Protactinium (Pa)
Protactinium (Pa, element 91) is an actinide in period 7. Atomic mass 231.036, electron configuration [Rn] 5f² 6d¹ 7s², uses and facts.
About Protactinium
Protactinium is an actinide with the symbol Pa and atomic number 91. It is a solid at room temperature, and it sits in period 7 of the periodic table. Protactinium was discovered in 1913 by Kasimir Fajans.
Protactinium key facts
- Atomic number: 91
- Symbol: Pa
- Atomic mass: 231.036 u
- Category: actinide
- Group: none (f-block)
- Period: 7
- State at room temperature: solid
- Electron configuration: [Rn] 5f² 6d¹ 7s²
- Electronegativity (Pauling): 1.5
- Melting point: 1841 K (1567.85 °C)
- Boiling point: 4300 K (4026.85 °C)
- Density: 15.37 g/cm³
- Common oxidation states: +2, +3, +4, +5
Electron configuration
The electron configuration of protactinium is [Rn] 5f² 6d¹ 7s². The part in brackets is the noble gas core; the rest shows how the outer electrons fill their subshells.
Uses of protactinium
- Research only
Did you know?
Protactinium is one of the rarest and most expensive elements, a gram costs hundreds of thousands of dollars.
Neighbouring elements
- Thorium (Th)
- Uranium (U)
- Actinium (Ac)
- Thorium (Th)
- Uranium (U)
- Neptunium (Np)
- Plutonium (Pu)
- Americium (Am)
- Curium (Cm)
- Berkelium (Bk)
Frequently asked questions
What is the atomic number of protactinium?
The atomic number of protactinium is 91, which means every protactinium atom has 91 protons.
What is the electron configuration of protactinium?
The electron configuration of protactinium is [Rn] 5f² 6d¹ 7s².
What group and period is protactinium in?
Protactinium is an actinide in period 7.
What state is protactinium at room temperature?
Protactinium is a solid at room temperature.
What is protactinium used for?
Protactinium is used for research only.