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Thorium (Th) – Element 90 of the periodic table

Thorium (symbol Th) is element number 90 of the periodic table and belongs to the “Actinide” category. Its atomic mass is about 232.04, and its phase under standard conditions is Solid. This element sits in period 7 and the f-block (Actinides) of the periodic table, and its electrons are arranged in shells of 2, 8, 18, 32, 18, 10, 2. The short electron configuration of Thorium is [Rn] 6d² 7s². Known uses of Thorium include Nuclear fuel, Welding electrodes and Optical glasses.

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Properties of Thorium

Atomic number
90
Chemical symbol
Th
Atomic mass
232.04
Category
Actinide
Period
7
Block
f
Phase
Solid
Protons
90
Electrons
90
Neutrons (approx.)
142
Electron shells
2, 8, 18, 32, 18, 10, 2
Outer-shell electrons
2
Discovered
Jöns Jacob Berzelius (1828)

Electron configuration of Thorium

The electron configuration of Thorium (Th), with 90 electrons, is shown below. The last shell (shell 7) is highlighted:

Full configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 6d² 7s²
Short configuration
[Rn] 6d² 7s²
Last shell
7s²

What is electron configuration and how is it written?

Electron shells of Thorium

Distribution of 90 electrons of Thorium across shells K to Q:

  1. K2
  2. L8
  3. M18
  4. N32
  5. O18
  6. P10
  7. Q2

What is a actinide?

The actinides are the 15 elements from actinium to lawrencium, part of the f-block, and all of them are radioactive.

Uses of Thorium

Frequently asked questions about Thorium

What is the atomic number of Thorium?

The atomic number of Thorium (Th) is 90; that is, every atom of it has 90 protons.

What is the electron configuration of Thorium?

The electron configuration of Thorium (Th) is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 6d² 7s²; in short form it is [Rn] 6d² 7s², and its last shell is 7s².

What is the chemical symbol of Thorium?

The chemical symbol of Thorium is Th.

Where is Thorium located in the periodic table?

Thorium is located in period 7 and the f-block (Actinides) and belongs to the “Actinide” category.

What is the atomic mass of Thorium?

The atomic mass of Thorium is about 232.04 (atomic mass units).

What is the phase of Thorium under normal conditions?

The phase of Thorium under standard conditions is Solid.

What are the uses of Thorium?

Uses of Thorium include Nuclear fuel, Welding electrodes and Optical glasses.

Who discovered Thorium?

Thorium was discovered by Jöns Jacob Berzelius in 1828.

Elements in the same category as Thorium (Actinide)

Actinium (Ac)Protactinium (Pa)Uranium (U)Neptunium (Np)Plutonium (Pu)Americium (Am)Curium (Cm)Berkelium (Bk)Californium (Cf)Einsteinium (Es)Fermium (Fm)Mendelevium (Md)Nobelium (No)Lawrencium (Lr)

See all Actinides