Radium

Radium is a special kind of chemical element with the symbol Ra and atomic number 88. It belongs to a group called the alkaline earth metals. Pure radium looks silvery-white, but it quickly changes when it touches air. All forms of radium give off invisible energy called ionizing radiation, which can make certain materials glow in the dark.

Radium was discovered in 1898 by Marie and Pierre Curie while studying materials from a mine in Jáchymov. They found it in a substance called uraninite. Later, in 1910, they separated the pure metal using a process called electrolysis. Though it was once used to make glow-in-the-dark paints and even sold as a health treatment, radium is now known to be very harmful. It is not used much today except in some special medical treatments.

Radium occurs naturally but only in very tiny amounts, mostly found along with uranium ores. It is not needed by living things and can be dangerous because its radioactivity can harm the body. Today, safer materials have replaced radium in most everyday uses.

Bulk properties

Radium is a very heavy type of metal called an alkaline earth metal. It is special because it gives off radioactive energy. It looks most like barium, which is another metal in the same group.

Pure radium looks silvery-white and shiny. But when you let it touch air, its surface quickly turns black. This happens because it reacts with something in the air to make a compound called radium nitride (Ra₃N₂). Radium melts at around 700–960 °C and boils at about 1,737 °C. It is a bit lighter than some similar metals but heavier than barium. It has a dense, strong structure like other metals in its group.

Isotopes

Main article: Isotopes of radium

Radium has 33 known forms, called isotopes, and all of them are radioactive. Four of these occur naturally because they are created when bigger elements break apart. They have short lifetimes, ranging from a few days to a few thousand years.

The most stable isotope of radium is ²²⁶Ra, with a lifetime of over 1,600 years. It makes up almost all of the radium found in nature. When it breaks apart, it creates a gas called radon, which can be dangerous. Radium gives off heat and particles as it changes, and some of its forms have special shapes that scientists study.

Chemistry

Radium has only one common form when it is dissolved in water. It creates a simple, clear substance called Ra²⁺ that does not mix easily with other substances. Because of this, most radium compounds are straightforward and do not connect with many other chemicals.

Radium compounds start out white but slowly change color over time because of the energy they release as they break down. Radium mixes with water to form a substance called radium hydroxide, which is very soluble and a strong base. Radium also forms compounds like radium chloride and radium bromide, which are clear and can glow because of the energy radium gives off. These compounds can change color or even break apart because of the strong energy radium releases. Radium also creates insoluble salts, such as radium sulfate, which do not dissolve easily in water and are among the least harmful radium compounds because of this property.

Occurrence

Radium does not stay on Earth for a very long time because it changes quickly into other substances. However, we can still find tiny amounts of it in nature. This happens because it is made when other elements, like thorium and uranium, change over time. These elements last much longer, so radium is always being made again.

The most common type of radium is called ²²⁶Ra. It is found in very small pieces in rocks that contain uranium, such as uraninite and other uranium minerals. It is also in even smaller amounts in rocks that contain thorium. For example, one big piece (ton) of a uranium-containing rock called pitchblende usually has about one seventh of a gram of radium.

History

Further information: Marie Curie § New elements

Radium was discovered by Marie Skłodowska-Curie and her husband Pierre Curie on 21 December 1898. They found it in a sample of uraninite from Jáchymov. While studying the mineral, they removed uranium and found the remaining material was still radioactive. They isolated an element similar to bismuth, which turned out to be polonium. Later, they found a radioactive mixture that looked like barium but was less soluble. This led to the discovery of a new element. They announced their discovery to the French Academy of Sciences on 26 December 1898. The name "radium" comes from the Latin word for "ray," because it gives off energy in the form of rays.

In 1910, Marie Curie and André-Louis Debierne succeeded in isolating radium as a pure metal. They used a process called electrolysis on radium chloride. Later that year, another scientist isolated radium using a different method. Radium became an important material in the early 1900s and was exported from Belgium until World War II.

The unit of measurement for radioactivity, the curie, is based on the radioactivity of ²²⁶Ra. It was originally defined using one gram of radium-226 but was later changed to a specific number of disintegrations per second.

Historical applications

Luminescent paint

Radium was once used in special paints that glowed in the dark for watches, clocks, and aircraft instruments. These paints contained a tiny amount of radium. However, some workers who applied the paint got very sick because they were instructed to lick their brushes to point them, which led to them swallowing radium. This caused serious health problems. After learning about these dangers, safer practices were introduced, and radium paint was eventually replaced with safer materials.

Clocks and watches from the early 1900s might have used this glowing paint. Over time, they stopped glowing not because the radium disappeared (it lasts a very long time), but because the material that made it glow wore out. The paint often changed color over the years.

Use in electron tubes

Radium was used inside special glass tubes called electron tubes. A small amount of radium helped the tubes work better by creating a path for electricity. The radium was sealed inside the tube, so it didn’t pose a danger.

Quackery

Radium was once added to many everyday products like soap, cosmetics, and even drinks because people believed it had healing powers. These products were often advertised falsely. When it was discovered that they could be harmful, they were banned in many places. Some spas still claim benefits from radium-rich water, but the radioactivity may come from other sources.

Medical and research uses

Radium was used in medicine to create a gas called radon, which was used to treat cancer. However, these treatments are no longer used because they were found to be harmful. Today, safer materials are used instead.

Radium was also used in the past to treat hearing problems in children and for other medical purposes, but these uses have stopped because they were found to be unsafe.

In the early 1900s, scientists used radium to study changes in animals and learn about genetics. Some famous experiments involved fruit flies.

Production

In the past, uranium was mainly found in silver mines in Jáchymov, which is now part of the Czech Republic. Scientists like Marie and Pierre Curie used these uranium leftovers to find radium. They boiled the leftovers and used special liquids to clean and separate the radium.

Later, other countries wanted radium too, so they searched for more uranium. The United States became a big producer in the early 1910s. Even today, radium is mostly taken from used nuclear fuel. By 1954, the whole world had only about 5 pounds of purified radium. Over time, production got smaller, and today it is very limited.

Modern applications

Radium is now being used more in the study of atoms and light. Because it is a heavy element, it helps scientists look for new discoveries beyond what we normally understand about the building blocks of the universe. Some forms of radium, like radium-225, are especially good at spotting very tiny changes that could show us new physics.

Radium is also being looked at for use in very precise timekeeping devices called optical clocks. These clocks could be smaller and easier to move around because they use special light signals that are easy to create with common tools.

Though radium has been used for medical treatments and in some industrial tools, newer materials like cobalt-60 and caesium-137 are now preferred because they are safer and stronger. In 2013, a special form of radium called radium-223 was approved to help treat certain types of cancer that spread to the bones. Scientists also continue to explore radium for its possible use in medical experiments.

Hazards

Radium is very radioactive, just like the gas it creates called radon. If someone swallows radium, about 80% of it leaves the body, but the remaining 20% goes into the blood and collects in the bones. The body thinks radium is like calcium, so it puts it in bones, where the radioactivity can harm the soft parts inside bones and change bone cells. Being near radium, whether inside or outside the body, can lead to cancer and other health problems because radium and radon give off rays that damage and change cells.

One of the first known health issues from radium happened in 1900. A scientist carried a small container of radium in his pocket for a few hours, and his skin became sore and damaged. Another scientist put radium on his arm for ten hours, and it caused a sore spot on his skin. Radium’s danger also comes from radon gas, which can easily get into the body.

Regulation

Rules to protect people from radium and radiation were first suggested in 1928 by a group of scientists and have been used around the world ever since. Groups like the International Commission on Radiological Protection and the World Health Organization still make and follow these rules today. The International Atomic Energy Agency also gives advice on how to handle radium safely. Countries have their own extra rules too. For example, in the United States, there are limits on how much radium can be in drinking water. During a big science project in the 1940s, rules were set for how much radium workers could handle. Different groups in each country manage these rules to keep everyone safe.