91
Pa
231.04
Protactinium (Pa)
Element 91 · Period 7 · Actinide series
actinide
solid at room temp
f-block
radioactive
About Protactinium
Rare radioactive metal. Intermediate in uranium-235 decay chain.
Physical Properties
Atomic Mass
231.04 u
State at 25°C
Solid
Melting Point
1568 °C
Boiling Point
4027 °C
Density
15.37 g/cm³
Magnetism
Paramagnetic
Atomic Properties
Electron Configuration
[Rn] 5f² 6d¹ 7s²
Electron Shells
2, 8, 18, 32, 20, 9, 2
Electronegativity
1.5
Atomic Radius
243 pm
Ionization Energy
568 kJ/mol
Oxidation States
+4, +5
Discovery & History
Discovered By
Kasimir Fajans
Discovery Year
1913
Named By
Otto Hahn
Name origin: Greek: protos (first) + actinium
Frequently Asked Questions
- Is Protactinium a metal, nonmetal, or metalloid?
- Protactinium is classified as a actinide.
- What state is Protactinium in at room temperature?
- Protactinium is a solid at standard room temperature (25°C).
- What is the atomic mass of Protactinium?
- Protactinium has an atomic mass of 231.04 atomic mass units (u).
- Who discovered Protactinium?
- Protactinium was discovered by Kasimir Fajans in 1913.
- Where is Protactinium on the periodic table?
- Protactinium is element number 91, located in period 7, part of the actinide series shown below the main table.