About

Protactinium is a dense, silvery-gray radioactive actinide metal that is one of the rarest and most expensive naturally occurring elements. It is primarily extracted from spent nuclear fuel. Due to its scarcity, toxicity, and high radioactivity, it currently has no uses outside of fundamental scientific research. It is a superconductor at low temperatures.

Atomic Properties

Atomic Number91

Atomic Weight231.036 u

Neutrons (common)140

Electron Configuration[Rn] 5f² 6d¹ 7s²

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 5f² 6d¹ 7s²

Electrons per Shell2, 8, 18, 32, 20, 9, 2

Electronegativity1.5

Electron Affinity53.03 kJ/mol

Oxidation States+5, +4, +3, +2

Covalent Radius180 pm

Ionic Radius96 pm

Periodic Table Position

Group3

Period7

BlockF

Chemical SeriesActinoids

Physical Properties

State at STPsolid

Appearancebright, silvery metallic lustre that slowly tarnishes in air

Crystal Structuretetragonal

Magnetic Orderingparamagnetic

Thermal Properties

Melting Point1,841 K

Boiling Point4,300 K

Thermal Expansion0 1/K

Thermal Conductivity47 W/(m·K)

Specific Heat0.121 J/(g·K)

Molar Heat27.96 J/(mol·K)

Heat of Fusion12.34 kJ/mol

Heat of Vaporization481 kJ/mol

Abundance

In Earth's Crust0 ppm

In Ocean0 ppm

Discovery

Discovered byKasimir Fajans, Oswald Helmuth Göhring

Discovery Year1,913

Occurrencefrom_decay

CAS Number7440-13-3

Electron Configuration

Energy

↿⇂

1s

↿⇂

2s

↿⇂

2p

↿⇂

3s

↿⇂

3p

↿⇂

4s

↿⇂

3d

↿⇂

4p

↿⇂

5s

↿⇂

4d

↿⇂

5p

↿⇂

6s

↿⇂

4f

↿⇂

5d

↿⇂

6p

↿⇂

7s

↿

5f

↿

6d

7p

Isotopes of Protactinium

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
²³¹Pa	231.035880	Trace	32.65 ky	Alpha Decay