The Rare Element Radium

radium clock

Introduction to the Element Radium

Radium is an incredibly rare and highly radioactive element with remarkable properties. Discovered by Marie and Pierre Curie in 1898, it is a silvery-white metal that emits a faint blue glow due to its radioactivity. Radium’s intense radioactivity makes it a highly sought-after element in certain areas of research. However, despite its dangerous nature, radium has found applications in medicine, specifically cancer treatment. Read on to learn more about Radium!

Ten Radiant Facts about Radium

  • Radium is the only radioactive alkaline-earth metal.
  • Pure radium is a volatile silvery-white metal.
  • The compound 223Ra dichloride treats certain types of cancer, including prostate cancer.
  • Radium was the first radioactive element to be discovered.
  • Radium was once used in cosmetics for its luminous properties, which made products glow in the dark.
  • Radium established a unit of radioactivity called the Curie. One Curie is equal to the radioactive activity of one gram of radium-226.
  • Radium’s radioactive decay produces radon gas, which is also hazardous.
  • Radium has a high density, approximately 2.8 times that of water.
  • Uranium ores naturally contain radium, such as pitchblende.
  • The element radium has a strong affinity for sulfur, forming compounds such as radium sulfate. This is useful in the extraction and isolation process of radium.

Radium on the Periodic Table

The symbol Ra represents radium. The atomic number is 88, which means there are 88 protons within the nucleus of a radium atom. In its neutral state, radium possesses 88 electrons distributed around the nucleus. Radium has several isotopes, but its most stable and abundant isotope is radium-226, which contains 138 neutrons in its nucleus.

As a member of Group 2 on the periodic table, radium falls under the classification of alkaline earth metals. This group includes elements like beryllium, magnesium, and calcium. Positioned in period 7, radium is situated in the s-block of the periodic table. The s-block encompasses the alkali metals, alkaline earth metals, and the nonmetals hydrogen and helium. With an electron configuration of [Rn] 7s², radium possesses two valence electrons. On the Pauling electronegativity scale, radium has a relatively small electronegativity value of approximately 0.9.

Radium Applications in Today’s World

In medicine, radium treats cancer. Compounds of Radium-based isotopes, such as radium-223, alleviate pain and increase the survival rate in patients suffering from bone metastases. Another application is for industrial radiography. Radium works as a gamma radiation source for inspecting the properties of materials. In the oil and gas industry, radium is used to check the integrity of pipelines.

Discovery of Radium

In 1898 the French scientists Marie Curie and Pierre Curie discovered radium. Therefore, radium is the oldest radioactive element discovered! Studying a sample of the mineral Pitchblende, already known to contain uranium, the Curies noticed that the pitchblende was four to five times more radioactive than the amount of uranium it contained would have allowed, meaning there must have been a more radioactive element in the mineral. The Curies calculated the atomic weight of Radium to be 225.2, remarkably close to the accepted value of 226 today! By 1902 they had succeeded in isolating a tiny amount of pure radium chloride.

The Radium Girls

In the early 20th century, radium gained popularity as an ingredient in the cosmetics industry. Face creams, powders, and even toothpaste that contained radium were marketed as the epitome of modern beauty. The trend reached its peak in the 1920s in what was called the “Radium Age”. However, people were unaware of the long-term health consequences of radium exposure. Tragically, those working in radium-based cosmetic factories as well as individuals who used these products experienced severe health issues.

One notorious example is the “Radium Girls” case. During the First World War being able to access and view watches in the dark trenches was vital. The glow in the dark luminescent paint that was used on these watches was a mixture of zinc sulphide and radium. Women working in factories in the U.S. painting these watches had to use precise camelhair brushes to apply the water-based paint. These brushes required workers to place the brush between their lips to form a fine point every time they dipped their brushes in the paint, causing them to ingest a little bit of radium each time. Beginning in the 1920s, however, many workers in these factories began to complain of ailments.

Radium painters at work in a factory. They sit in rows under a low ceiling painting.
Radium painters at work in a factory

By the mid-1920s, a clear link was established between exposure to radium and many of the horrific symptoms that workers in these factories endured. In 1927, the five surviving Radium Girls filed a lawsuit against their previous employer, but, fearing they wouldn’t survive a lengthy trial, later settled for a payment. The entirely avoidable deaths of the Radium girls serve as a grim reminder of the importance of protecting workers’ rights and prioritizing workplace safety.

For more in depth reporting on this topic, Kate Moore wrote a great book, “The Radium Girls”.

Radioactivity of Radium

Radium compounds emit alpha particles which excite electrons in the other elements in the compound. The electrons release energy as light when they de-excite. One gram of radium-226 undergoes 3.7E10 disintegrations per second. This unit was coined the Curie. This is an energy release equivalent to about 6.8E-3 calorie per second.

Radium Compounds

Radium Chloride (RaCl₂)

Used in medical treatments, especially cancer treatments. It is a colorless solid that glows blue-green. The end result of the Curie method of radium isolation (scroll down for more info).

Radium Sulfate (RaSO₄)

This white salt is the least soluble of all known sulfate salts. It was formerly used in radiotherapy and smoke detectors, but has been phased out in favor of less hazardous alternatives.

Radium Bromide (RaBr₂)

A luminous salt that causes the air surrounding it, even when encased in a tube, to glow a brilliant green. Radium bromide was used in dials and watch hands, as well as in many cosmetics in the early 20th century.

Radium Carbonate (RaCO₃)

The salt radium carbonate is a poisonous and radioactive white powder that is used in medicine.

    \begin{align*}{Ra^{2+} + CO_3^{2-} \rightarrow RaCO_3}\end{align*}

Radium Hydroxide (Ra(OH)₂)

Formed by the reaction of radium metal with water. A caustic, toxic, and corrosive substance.

    \begin{align*}{Ra + 2 H_2O \rightarrow Ra(OH)_2 + H_2}\end{align*}

Radium Oxide (RaO)

Formed by the reaction of radium metal with oxygen gas. A precursor to the formation of other radium compounds.

    \begin{align*}{2 Ra + O_2 \rightarrow 2 RaO}\end{align*}

Radium Oxidation State

The most common oxidation state (also known as oxidation number) of radium is +2; Radium belongs to Group 2 elements, also known as alkaline earth metals, and tends to lose two electrons to achieve a stable configuration.

Radium Isolation

The radium isolation process involves many steps and is a complicated procedure. The “Curie” method consists of two major stages. The first stage is treating pitchblende to concentrate the radium as a combination of radium and barium. In this stage barium salt and sulfuric acid are applied to the ore and get rid of most elements present, leaving mainly barium and radium. The next stage uses a process known as fractional crystallization to separate the barium from the radium. The end result of this process is crystals of radium bromide. Afterwards (as well as during the entire process) scientist measure radioactivity to ensure safety and to quantify the radium content being extracted.

A raw sample of pitchblende, also known as uraninite, a radium and uranium containing ore. It is yellow-green and rough.
A raw sample of pitchblende, also known as uraninite, a radium and uranium containing ore.

Physical properties of the Element Radium

  • Symbol: Ra
  • Melting point: 700°C
  • Boiling point: 1,737 °C
  • Density (g cm−3): 5.5
  • Atomic mass: 226 amu
  • Atomic number: 88
  • Electronegativity (Pauling Scale): 0.89
  • Classification: Alkaline earth metal, Group II metal
  • Electron configuration: [Rn] 7s²
  • Key Isotopes: There are twenty-five isotopes, four of which are found in nature: 223Ra, 224Ra, 226Ra, and 228Ra
  • Radium is found in small amounts in all uranium-bearing rocks, as it is formed in the decay of uranium.
  • Toxicity: Exposure to any form of Radium for humans may result in an increased risk of certain types of cancer.

Where Can I Buy Elemental Radium?

The element radium is highly regulated and extremely hazardous, meaning it is not available for purchase by the public. However, Radium-based paint coated products, sealed in ampules and coated in resin for safety, are available from some novelty chemical suppliers such as Nova Elements.

If you want to learn about other elements, check out our INTERACTIVE PERIODIC TABLE!