91 Pa Protactinium 231.04 u

Protactinium

Period
7
Group
—
Block
f-block
Phase (STP)
Solid

Protactinium is a scarce, radioactive actinide. It is one of the rarest and most expensive naturally occurring elements.

About Protactinium

Scarcity and cost define protactinium's place among the naturally occurring elements; it ranks with the rarest and the most expensive of them. Atomic number 91 and a relative atomic mass of 231.04 place it between thorium and uranium in the actinide series, and its configuration [Rn] 5f2 6d1 7s2 shows the 5f subshell beginning to fill. The Pauling electronegativity is 1.5, the highest among the early actinides, and the element is a solid under standard conditions. Because it is radioactive and occurs only in minute quantities within uranium ores, protactinium has no bulk industrial use. Its chemistry is studied instead for what the filling of the 5f orbitals reveals about bonding across the f-block.

Physical Properties

Atomic Mass 231.04 u
Phase at STP Solid

Electronic Properties

Electronegativity 1.5

Electron Configuration

Configuration [Rn] 5f² 6d¹ 7s²

Electron Shell Configuration

Protactinium electron shell configuration Pa 2e⁻ 8e⁻ 18e⁻ 32e⁻ 20e⁻ 9e⁻ 2e⁻
Electron shell structure of Protactinium — electrons per shell.
Shell Electrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 32
5 (O) 20
6 (P) 9
7 (Q) 2

Position in Periodic Table

Protactinium position in the periodic table Pa

Block & Period

Block

s p d f

Period

1 2 3 4 5 6 7

Periodic Table

Lanthanides Actinides

More Actinide

89 Ac Actinium 90 Th Thorium 92 U Uranium 93 Np Neptunium 94 Pu Plutonium 95 Am Americium 96 Cm Curium 97 Bk Berkelium 98 Cf Californium 99 Es Einsteinium

Frequently Asked Questions

What is Protactinium?
Protactinium (Pa) is a chemical element with atomic number 91. It is a solid at standard temperature and pressure, classified as a actinide.
What are the key properties of Protactinium?
Protactinium has an atomic mass of 231.04 u.
What is the electron configuration of Protactinium?
The electron configuration of Protactinium is [Rn] 5f2 6d1 7s2. It is in the f-block of the periodic table.
What is the electronegativity of Protactinium?
Protactinium has an electronegativity of 1.5 on the Pauling scale.