Here Are The Chemical Properties Of Thorium

Group  - Actinides 

Period – 7

Block – f

Atomic number – 90

State at 20°C – Solid

Electron configuration - [Rn] 6d27s2 

Melting point - 1750°C, 3182°F,2023K

Boiling point - 4785°C, 8645°F , 5058K

Density (g cm−3) - 11.7 

Relative atomic mass - 232.038  

Key isotopes - 230Th, 232Th 

CAS number  - 7440-29-1 

Thorium – What is it?

Thorium belongs to the actinide family. These are the elements that are placed on Row7 of the periodic table. The actinides have an atomic number between 90 and 103.

Thorium is an element that was discovered by a Swedish chemist named Jons Jakob Berzelius in the year 1828. He, however, did not know what thorium is and that it is a radioactive element. This was discovered in 1898 by Marie Curie, who was a Polish-French physicist as well as by Gerhard C. Schmidt, who was an English chemist.

Berzelius found a new element in the Falun district in Sweden, and he knew that it was a new element. The name thorium came in honour or the Scandinavian god Thor.

Here are The Physical Properties of Thorium

Thorium is a soft and silvery-white metal which looks somewhat like lead. It can be bent, cut, rolled, hammered, shaped or welded easily.

The physical properties of thorium are similar to that of lead. The melting point of thorium is 1,800°C (3,300°F), and its boiling point is 4,500°C (8,100°F). The density of thorium is 11.7 grams per cubic centimeter.

The pure form of thorium is air-stable, and it can retain its luster for many months. However, when thorium gets contaminated with oxide, then it starts to tarnish in air, and this changes its colour to grey and then to black. The melting point of thorium is one of the highest among all the oxides.

Thorium is attacked only slowly with water. However, it does not dissolve in most of the acids easily. This is except in hydrochloric acid. The powdered form of thorium is pyrophoric, and it should be handled with care. When thorium is heated in the air, then it burns with a bright white light.

Thorium – Its Applications

  • Before the radioactive property of thorium was known, there was a lot of retail use of thorium and its compounds. It was used in toothpaste and gas mantles. 

  • Thorium is still used in magnesium as an alloying element. It is used to cast the tungsten wire and finds use in the electronic equipment to control the plutonium grain size that finds application in the electric lamps.

  • Thorium is also used in the metallurgical industries in the manufacture of refractory materials. 

  • Thorium oxide also finds use in the laboratory cubicles with a high temperature. 

  • Thorium, when added to the glass, creates a glass that has a high refractive index and a low dispersion.

  • It is being studied to use thorium as a source of nuclear fuel. Thorium will find use in the nuclear reactor to burn it without generating plutonium. Thorium is also used to date the hominid fossils.


Thorium – Its Health Effects

Thorium is present everywhere on earth, and thus people are always exposed to it in small amounts. We get exposed to thorium energy through water, air and the food that we eat.


  • Large amounts of uncontrolled thorium could be found near the waste sites where the thorium has not been disposed of as per the proper procedure. This is hazardous. Those who live close to these sites are exposed to high amounts of thorium because they breathe more thorium and also have food that is grown in the site, which is high in thorium.

  • Those who work in the thorium, milling and mining industries are also exposed to thorium which is more than the natural exposure.

  • Breathing excess thorium could cause lung diseases and pancreatic cancer. Thorium can also change one's genetic materials. 

  • Those who have been injected with thorium, for some special x-ray could also develop liver disease.

  • Thorium is radioactive in nature, and it thus gets stored in the bones. This is why exposure to thorium can cause bone cancer. These harmful health effects are seen many years of being exposed to thorium.

  • If one breathes massive amounts of thorium, then this could be lethal for one's health. People could die because of metal poisoning when there is massive exposure to thorium.

FAQ (Frequently Asked Questions)

1. How does thorium react with the environment?

Thorium reacts with oxygen, water and the other compounds to form many tungsten compounds.

2. What is the biological role of thorium?

There is no known biological role of thorium because of its radioactivity property that makes it toxic.

3. How is thorium found in nature?

Thorium is found as thorianite, thorite and uranothorite minerals. This is the most important commercial source of thorium. Thorium is found as minerals and in the monazite which is its important commercial source.

4. How does thorium affect plants and animals?

Because of the size and the form of thorium there is no unusual environmental effect of thorium on plants and animals. However, if the thorium release is in large quantities then this will harm animals and plants.