What Makes Thorium Essential in Modern Chemistry?
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.
FAQs on Thorium: Properties, Applications & Importance
1. What is Thorium and where is it primarily found?
Thorium (Th) is a naturally occurring, weakly radioactive metallic element with atomic number 90. It belongs to the actinide series of the periodic table. Thorium is not found free in nature but is present in several minerals, most importantly in monazite sands, which are a primary commercial source. It is also found in minerals like thorite and thorianite.
2. What are the main physical properties of Thorium?
In its pure form, Thorium is a bright, silvery-white metal that is soft, malleable, and ductile. Its key physical properties include:
- Appearance: Tarnishes slowly in air to a grey, and eventually black, colour due to the formation of thorium dioxide (ThO₂).
- Melting Point: It has a very high melting point of approximately 1750°C.
- Boiling Point: Its boiling point is around 4790°C.
- Density: It is a dense metal with a density of about 11.7 g/cm³.
- Radioactivity: It is weakly radioactive, with its most stable isotope, Thorium-232, having a half-life of over 14 billion years.
3. What are the key chemical properties of Thorium?
Thorium is a reactive electropositive metal. Its most stable and common oxidation state is +4. When finely divided, thorium powder can be pyrophoric, meaning it can ignite spontaneously in air. It reacts slowly with water but dissolves readily in most common acids like hydrochloric acid. It forms a protective oxide layer that makes it stable in air for several months.
4. What are the most important applications of Thorium?
Thorium has several significant industrial and potential applications:
- Nuclear Fuel: It is a 'fertile' material that can be converted into the fissile isotope Uranium-233, making it a promising fuel for nuclear reactors.
- High-Strength Alloys: It is used to create magnesium-thorium alloys for the aerospace industry due to their high strength and creep resistance at elevated temperatures.
- High-Quality Optics: Thorium oxide (thoria) is used in high-quality lenses for cameras and scientific instruments because it imparts a high refractive index and low dispersion.
- Gas Mantles: Historically, it was widely used in incandescent gas mantles, which glow brightly when heated.
5. What is the electron configuration of Thorium?
The ground-state electron configuration of Thorium (Th) is [Rn] 6d² 7s². Unlike many other actinides where the 5f orbitals are filled, Thorium has no 5f electrons in its ground state. This configuration is a key reason for its chemical properties, particularly its dominant +4 oxidation state, which results from the loss of the 6d and 7s electrons.
6. Why is Thorium considered a 'fertile' material and not 'fissile' like Uranium-235?
The distinction between 'fertile' and 'fissile' is crucial in nuclear chemistry. A fissile material, like Uranium-235, can sustain a nuclear chain reaction on its own upon capturing a neutron. In contrast, a fertile material, like Thorium-232, cannot sustain a chain reaction by itself. However, when it absorbs a neutron, it transmutes into a fissile isotope. Thorium-232 absorbs a neutron to become Thorium-233, which then decays to Protactinium-233 and finally to the fissile isotope Uranium-233. This U-233 can then be used as fuel.
7. How does Thorium's radioactivity affect its handling and biological role?
Thorium has no known biological role and is considered toxic due to its radioactivity and heavy metal properties. While solid thorium metal is relatively safe to handle with basic precautions due to its weak alpha radiation, its dust and compounds can be hazardous if inhaled or ingested. The alpha particles it emits can cause significant damage to internal tissues, primarily the lungs, bones, and liver, increasing the risk of cancers. Therefore, proper ventilation and protective measures are essential when working with powdered thorium or its compounds.
8. What makes Thorium a potentially safer and more abundant alternative to Uranium for nuclear energy?
Thorium is considered a promising alternative to uranium for several reasons:
- Abundance: Thorium is estimated to be about three to four times more abundant than uranium in the Earth's crust.
- Less Long-Lived Waste: Thorium-based fuel cycles produce significantly less long-lived transuranic waste (like plutonium and americium) compared to uranium fuel cycles.
- Proliferation Resistance: The byproducts of the thorium fuel cycle are more difficult to weaponise, making it a more proliferation-resistant option.
- Inherent Safety: Certain designs of thorium reactors, such as Molten Salt Reactors (MSRs), have inherent safety features that can prevent meltdowns.
9. What is the significance of the +4 oxidation state for Thorium's chemistry?
The +4 oxidation state is the most dominant and stable state for Thorium, defining almost all of its known chemistry. This stability arises from its electron configuration ([Rn] 6d² 7s²), where it readily loses all four valence electrons to achieve a stable, noble gas-like configuration. As a result, Thorium chemistry largely resembles that of Group 4 transition metals like Zirconium (Zr) and Hafnium (Hf). This stable +4 state means Thorium forms highly stable compounds like Thorium dioxide (ThO₂) and is not easily reduced or oxidised to other states, making its chemistry less complex than many other actinides.
