Actinide

Protactinium

Protactinium (Pa) has atomic number 91. PubChem classifies it as actinide.

Atomic number

91

Symbol

Pa

Atomic weight (source value)

231.03588

Electron configuration

[Rn]7s2 5f2 6d1

Standard state

Solid

Electronegativity (Pauling)

1.5

Melting point (K)

1845

Boiling point (K)

Not provided

Density (g/cm³)

15.37

Oxidation states

+5, +4

Understanding this entry

Atomic number is the number of protons in the nucleus. Properties are reference values and may depend on conditions and measurement conventions. An atomic weight is not the mass of every isotope. For elements without a standard atomic weight, a source may report an isotope mass number. Blank source values are shown as unavailable rather than estimated.

Further reading and reference: NIH PubChem source dataset ↗. Values and educational summaries are not a substitute for specialised advice.