Protactinium

Actinide · atomic number 91

91231.035882PaProtactiniumSolidActinide

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.

Properties of Protactinium

Element category	Actinide
Atomic number	91
Atomic mass	231.035882 u
Phase at STP	Solid
Group	3
Period	7
Block	f
Electron configuration	[Rn] 5f2 6d1 7s2
Electrons per shell	2, 8, 18, 32, 20, 9, 2
Electronegativity (Pauling)	1.5
Melting point	1841 K (1568 °C)
Boiling point	4300 K (4027 °C)
Density	15.37 g/cm3
Discovered by	William Crookes
Named by	Otto Hahn

← Thorium · Periodic table · Uranium → U

About the actinide group

Mostly radioactive, heavy metals — several made only in reactors — whose fission powers nuclear energy and weapons.

Data: Periodic-Table-JSON (CC BY-SA 3.0) · stored statically on our server. https://en.wikipedia.org/wiki/Protactinium

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