Chemistry - Thorium

Introduction

• Thorium is one of the radioactive actinide metals that occur naturally in large quantities.

• The symbol of thorium is ‘Th’ and atomic number is ’90.’

• In 1829, a Norwegian mineralogist Morten Thrane Esmark, first discovered thorium.

• Jöns Jacob Berzelius, the Swedish chemist, identified and named it ‘thorium’ after the name of ‘Thor’, the Norse god of thunder.

Salient Features of Thorium

• Thorium is paramagnetic and soft radioactive actinide metal.

• Thorium metal’s color is silvery; when it exposed to air, it tarnishes black and form dioxide.

• All isotopes of thorium are unstable and it is a weak radioactive element.

• Among all the significant radioactive elements, the half-life of thorium is the longest, i.e. about 14.05 billion years.

• The melting point of thorium is about 1750⁰C.

Occurrence of Thorium

• Thorium is primordial element that exists existed in its current form since before the Earth was formed.

• Thorium, found in the earth’s crust, is refined from the monazite sands.

• Monazite that occurs in large amounts across the world is the most important source of thorium.

Alloys of Thorium

• Mag-Thor and thorium-aluminum are the most significant alloys of thorium, Magnesium, and aluminum.

Compounds of Thorium

• Following are the major compounds of Thorium −

  • Thorium dioxide - ThO₂

  • Thorium (IV) sulfide - ThS₂

  • Thorium (IV) iodide - ThI₄

  • Thorium tetrafluoride - ThF₄

  • Thorium (IV chloride - ThCl₄

  • Thorium (IV) carbide - ThC

• Some others are −

  • Thorite

  • Thorium (IV) nitrate

  • Thorium (IV) orthosilicate

Uses of Thorium

• Thorium is normally used in gas tungsten arc welding (GTAW) because it (thorium) increases the high-temperature strength of tungsten electrodes and accordingly improve arc stability.

• In electronic equipment, the application of thorium coating on tungsten wire, increases the electron emission of heated cathodes.

• In chemical industry, the dioxide of thorium namely ‘thoria’ is commonly used.