Is protactinium a metal?

Yes. Protactinium is a metal, classified as an actinide on the periodic table.

How many protons does protactinium have?

Protactinium has 91 protons. Its atomic number is 91, which is also the number of electrons in a neutral atom of protactinium.

What group and period is protactinium in?

Protactinium is in period 7 of the periodic table. As an actinide in the f-block, it sits in a separate row below the main table and has no standard group number.

What is the atomic mass of protactinium?

The atomic mass of protactinium is 231.04 u (unified atomic mass units).

Element 91

Protactinium (Pa)

Actinide · Period 7 · f-block

Protactinium (Pa) is element 91 of the periodic table, an actinide in period 7 (f-block) with an atomic mass of 231.04 and is a solid at standard conditions.

At a glance

Atomic number: 91
Symbol: Pa
Atomic mass: 231.04 u
Category: Actinides
Period: 7
Block: f-block
Phase at STP: solid

Electron structure

Electron configuration: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 5f2 6d1 7s2
Shorthand configuration: [Rn] 5f2 6d1 7s2
Electrons per shell: 2, 8, 18, 32, 20, 9, 2
Oxidation states: +2, +3, +4, +5

Physical properties

Melting point: 1,841 K (1,567.85 °C)
Boiling point: 4,300 K (4,026.85 °C)
Density: 15.37 g/cm³
Phase: solid

Atomic properties

Electronegativity (Pauling): 1.5
Atomic radius: 163 pm
Covalent radius: 200 pm
First ionization energy: 568 kJ/mol
Electron affinity: 53 kJ/mol

Notable isotopes

Notable isotopes of Protactinium: mass number, atomic mass, natural abundance, and stability.
Isotope	Mass	Abundance	Stability
Pa-231	231.03588	-	Half-life 32760 years

Common uses

Scientific research only

Discovery

Year: 1913
Discovered by: Kasimir Fajans, Oswald Helmuth Göhring
Country: Germany

Frequently asked questions

Is protactinium a metal?: Yes. Protactinium is a metal, classified as an actinide on the periodic table.
How many protons does protactinium have?: Protactinium has 91 protons. Its atomic number is 91, which is also the number of electrons in a neutral atom of protactinium.
What group and period is protactinium in?: Protactinium is in period 7 of the periodic table. As an actinide in the f-block, it sits in a separate row below the main table and has no standard group number.
What is the atomic mass of protactinium?: The atomic mass of protactinium is 231.04 u (unified atomic mass units).

Keep exploring

Protactinium's row is on the printable element property sheet, and its tile is on the periodic table wall chart - the same numbers as above, laid out for A4 or A3 paper.