Radium Ra

Discovery

In December 1898 Marie and Pierre Curie, with their assistant Gustave Bémont, announced a new radioactive element that separated together with barium from pitchblende, five months after polonium. To obtain a pure radium salt Marie Curie spent years processing tonnes of ore residue in a shed-like laboratory, and in 1902 she obtained about 0.1 g of radium chloride and determined its atomic weight.

In 1910 Marie Curie and André-Louis Debierne isolated radium metal for the first time by electrolysing a radium chloride solution. The following year Marie Curie received the Nobel Prize in Chemistry for the discovery of polonium and radium, becoming the first person to win Nobel Prizes in two sciences. The curie, a unit of radioactivity, was originally based on the activity of one gram of radium-226.

Origin of the name

The name comes from the Latin radius, meaning "ray", reflecting the strong radiation it emits.

Main uses

• Modern medicine: radium-223 is used to treat castration-resistant prostate cancer that has spread to bone. Because radium behaves like calcium, it concentrates around bone metastases and irradiates them with alpha particles.
• Historical cancer therapy: radium sealed in needles or tubes and placed near tumours was a major form of brachytherapy in the first half of the twentieth century.
• Historical luminous paint: radium mixed with a phosphor made watch and instrument dials glow; it has since been replaced by tritium or photoluminescent pigments.
• Historical neutron sources: radium-beryllium sources supplied neutrons for early nuclear-physics experiments and oil-well logging.

Isotopes

All radium isotopes are radioactive. The longest-lived, radium-226, has a half-life of about 1,600 years and is part of the uranium-238 decay chain; its decay produces radon-222 gas. Medical radium-223 has a half-life of about 11.4 days, and radium-228 from the thorium series about 5.75 years.

In everyday life

In the 1910s and 1920s young women painting watch dials with radium paint in the United States were taught to point their brushes with their lips. Many swallowed radium and suffered bone necrosis of the jaw, anaemia and cancer. Their lawsuits, remembered as the story of the "Radium Girls", helped establish employer responsibility for occupational disease and modern workplace safety standards. At the time, radium-laced water, cosmetics and tonics were also sold. Old luminous watches and gauges may still contain radium and should not be opened; ask a specialist service for advice on disposal.