Thorium

Thorium

Thorium is a chemical element with the symbol Th and atomic number 90. It is a weakly radioactive metal that looks silver and turns olive grey when it touches air. Thorium is soft, easy to shape, and can stay solid at high temperatures because it has a high melting point.

All forms of thorium are unstable. The most common form, ²³²Th, changes very slowly over 14.0 billion years, which is about the age of the universe. It goes through steps called the thorium series until it becomes a stable form of lead. On Earth, thorium and uranium are the only elements that do not have stable forms but still exist naturally in large amounts. Thorium is found more often in the Earth's crust than uranium. It is mostly found in sands called monazite when people are getting rare-earth elements.

Thorium was discovered in 1828 by the Swedish chemist Jöns Jacob Berzelius. He found it in a mineral from Norway and named it after Thor, the Norse god of thunder. Thorium had many uses in the past, like in welding and lighting, but these uses stopped because of worries about its radioactivity. Today, thorium is still used in some special ways, such as to make magnesium stronger and in certain nuclear reactors. Scientists also study thorium to learn more about ancient oceans.

Bulk properties

Thorium is a soft, shiny, and radioactive metal that can be bent or shaped easily. It is found in the periodic table between actinium and protactinium, and below cerium. Pure thorium can be stretched and shaped into different forms.

Thorium is not very dense and is harder than some other similar metals. It has a high melting point, much hotter than many other metals, and it can stay strong even when heated. The way thorium behaves can change a little depending on tiny amounts of other materials mixed in, but it usually stays fairly consistent in its properties.

Isotopes

Main article: Isotopes of thorium

There are seven natural types of thorium, but none are stable. ²³²Th is the main type found in nature, with a very long life—about 14 billion years. This makes it one of the longest-lasting radioactive elements found on Earth.

Thorium can lose atoms through a process called alpha decay, starting a chain that ends with a stable form of lead. This decay chain creates traces of other elements like lead, bismuth, and radon. Some of these decay products have uses in medicine. Scientists also study thorium for possible use in very accurate clocks and to learn about the age of old materials like coral and cave formations.

Chemistry

Thorium is a reactive metal. If it is broken into very small pieces and left in air, it can catch fire. In larger pieces, it changes slowly when left in air, turning gray and then black on the surface over time.

Thorium does not dissolve easily in water but will dissolve in some acids. It forms compounds with many other elements, such as oxygen, sulfur, and halogens like chlorine and fluorine. These compounds have different properties and uses. Some are very heat-resistant and have been studied for use in nuclear energy.

Occurrence

Main article: Occurrence of thorium

Thorium is a rare element in space. It forms during big explosions in stars called supernovae and when neutron stars crash together. These events spread thorium across space.

On Earth, thorium is more common. It is found in small amounts in many rocks and minerals. One important source is a mineral called monazite, which contains about 2.5% thorium. Monazite is found in places like India, South Africa, Brazil, Australia, and Malaysia. Another mineral called thorite also contains thorium and was the first place thorium was discovered. Thorium stays in place in the environment because it does not dissolve easily in water.

History

In 1815, a scientist named Jöns Jacob Berzelius studied a special rock from Sweden. He thought he found a new element and named it "thorium" after Thor, the Norse god of thunder, but later learned he was wrong.

In 1828, a priest and rock expert named Morten Thrane Esmark found a black rock in Norway. He gave it to his father, who then passed it to Berzelius. Berzelius confirmed it was a new element and named the rock thorite.

Berzelius studied the new element and found it was very reactive. In 1914, two Dutch scientists finally separated the metal itself.

In 1898, scientists discovered thorium was radioactive—the same year radioactivity was first found in another element, uranium. Later studies showed thorium changes slowly into other elements over time.

Thorium was first used in 1885 in gas lamps, which gave off bright light when heated. It was also used in many other things, like special glasses and ceramics.

Today, thorium is being studied for use in nuclear power because it could provide a lot of energy and create less waste than other nuclear fuels. Some countries, like India and China, are working hard to use thorium in power plants in the future.

Production

See also: List of countries by thorium resources

Because we don't need much thorium, it is not mined by itself. Instead, it is taken from materials used to get rare earth elements, which are often made as a by-product from mining other minerals. Right now, most thorium comes from a material called monazite, but there are other sources that could be used if needed. We don't know much about where thorium can be found because there hasn't been much reason to look for it.

Making thorium involves gathering thorium-containing minerals, taking the thorium out of those minerals, cleaning it, and sometimes turning it into useful compounds like thorium dioxide.

There are two main types of minerals that contain thorium. The first type is found in certain rocks and are usually small in size. The second type is found where rivers meet the sea in mountainous areas. These deposits have thorium mixed with other heavy minerals. The way thorium is gathered depends on which type of deposit it comes from.

For the first type, the rocks are broken into small pieces and processed to separate the thorium. For the second type, which is often found in sand along coasts, special methods using magnets are used to purify it. In the past, thorium was made using a method with strong acids, but today a different method using sodium hydroxide is used because it gives a cleaner result, even though it costs more.

Concentration

Purification

To use thorium in nuclear technology, it needs to be very pure. This is done using special liquid solutions that can separate thorium from other elements.

Modern applications

Uses of thorium that do not involve its radioactivity have become less common since the 1950s because of worries about its radioactivity.

Most uses of thorium involve a compound called thorium dioxide, also known as "thoria". This compound can stay solid at very high temperatures—around 3300 °C (6000 °F)—which is higher than most other materials. Because of this, it helps keep flames solid and very bright, which is why thorium was used in old gas lamp mantles. When thorium is heated, it gives off light that we can see, making the flame very bright. Though thorium is still used in some mantles, it has been replaced by another material called yttrium since the late 1990s.

Thorium dioxide has been used to make strong wires for electronic tubes and X-ray machines. It also helps make special glass for cameras and scientific tools by changing how light passes through it. However, because thorium is radioactive, other materials that are not radioactive are now used instead.

Potential use for nuclear energy

Thorium can be used to create nuclear power. When thorium atoms absorb particles called neutrons, they change into another type of atom that can be used as fuel in a nuclear reactor. This is similar to how we use uranium today.

Using thorium has some benefits. There is more thorium available than uranium, and it could provide energy for a very long time. Thorium can also help make reactors safer and work better. However, there are challenges too. Some by-products from using thorium are hard to handle because they give off strong radiation. Also, using thorium needs more advanced technology than the methods we use today. Scientists are still studying these issues.

Hazards and health effects

Natural thorium decays very slowly, and the radiation it gives off cannot pass through our skin. Handling small amounts of thorium, like in gas lamps, is generally safe. However, breathing in thorium dust can increase the risk of certain health issues.

Thorium can build up inside the body over many years. Workers who handle thorium need to take special care to stay safe.