Atomic Number: 88
Relative Atomic Mass: 226.00
Category: Alkaline Earth Metal (Group 2)
Appearance: Silvery white metallic
Above: Image © istockphoto.com/3dalia
Radium is best known for its radioactivity, its eerie luminescent glow, and its contribution to a Nobel Prize. Found at the bottom of the second column of the periodic table, it is grouped with other alkaline earth metals such as magnesium, calcium, and strontium. Radium is a silvery white metal in its pure form, but forms radium nitride (Ra3N2) and turns black when exposed to air.
Discovery and uses
Radium was first discovered in 1898 by Marie and Pierre Curie, along with another element called Polonium. This discovery earned Marie Curie a Nobel Prize in Chemistry in 1911. Due to its radioactive properties, the element was called radium after the Latin word “radius”, meaning rays. At the time, little was know about the dangers of radioactivity, and radium excited the scientific community because it was the most radioactive atom ever discovered.
Radium dial: A clock face, the hands and numbers of which contain radium and therefore glow in the dark after being exposed to light. Click image to enlarge (Wikimedia Commons/Arma95)
Did you know? Isotopes are two or more versions of the same atom that have the same number of protons but different numbers of neutrons. They have different relative atomic weights but the same chemical properties.
Until the 1960s, luminescent radium was used in paint, usually for watches and clocks. The production of these “glow in the dark” timepieces caused the workers, mostly young women, to ingest large amounts of radium and experience serious health effects such as lymphoma and bone cancer.
During the same period, medicines and water crocks containing radium were marketed to the public, under the brand names Radithor and the Radium Ore Revigator. The idea was that the radiation in radium water could prevent illness, but it ended up causing health problems and the products were eventually discontinued.
Radium was also used as a source of radiation for cancer treatment, but it has been replaced by safer and more effective sources, such as Cobalt-60. Currently there are very few uses of radium because of its dangerous levels of radioactivity.
Did you know? Marie Curie was the first woman to win a Nobel Prize and the first person to win two different Nobel Prizes.
Radioactivity occurs when an element’s nucleus is unstable. In order to become more stable, the atom emits alpha particles (2 protons and 2 neutrons), beta particles (electrons), and gamma rays (high energy radiation). Imagine if you stuffed 20 people into an elevator—there would not be enough room and people would want to leave. People would continue to leave the elevator until the remaining occupants could fit comfortably inside and it became stable.
Radium-226, the element's most common isotope, emits both alpha and gamma radiation and has a half-life of 1600 years. The half-life of a radioactive element refers to the amount of time it takes for half of the sample to undergo radioactive decay. For example, if you started with 100 grams of radium-226, after 1600 years, only 50 grams would remain.
Decay chain: Radium-226 is one step in a decay chain that begins with uranium-238. Click image to enlarge (Wikimedia commons/Tosaka)
External exposure to alpha radiation is not very dangerous to humans, but it can cause damage if the radioactive material is ingested. Gamma radiation is harmful both externally and internally. Long-term exposure to these types of radiation can damage your DNA and increases the risk of cancer.
Did you know? Radium has been added to the tip of lightning rods to increase their ability to attract lightning.
Radium is just one step in a larger process. It is formed from the radioactive decay of uranium-238, and the decay chain continues through radon gas until it reaches the stable element lead-206. Radium occurs in very small amounts in all soil, rocks, and water, but since it is a decay product of uranium it is mostly found in uranium ore. For example, one tonne of a uranium ore called pitchblende contains about 0.15 grams of radium. Radon is a particularly dangerous product of the radium radioactive decay process, mostly because it is a gas and can collect inside buildings.
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The discovery of radium helped usher in a new area of nuclear chemistry. Although scientists now understand the dangers of radium and radioactivity, which restrict its practical applications, the discovery of the element revolutionized both modern chemistry and physics.
Websites with basic information on radium, its uses, and its dangers.
Information on identifying and using older devices such as wristwatches, clocks, marine compasses and aircraft instruments that contain radium-based, glow-in-the-dark paint.
Article on often-dangerous consumer products that contained radium.