(So named (Latin radius, "ray") in 1898, when it was discovered, by Pierre and Marie Curie and Gustave Bemont because it emits rays) A radioactive, metallic chemical element, the heaviest of the alkaline-earth metals, found in very small amounts in pitchblende and other minerals containing uranium. It undergoes spontaneous atomic disintegration through several stages, emitting alpha, beta, and gamma rays and finally forming an isotope of lead. Radium is used in neutron sources and in the treatment of cancer and other diseases. Salts of radium exhibit fluorescence, and were formerly used in luminous watch dials.
Symbol: Ra
Atomic number: 88
Atomic weight: 226 (
isotope with the longest known
half-life)
Density (at
room temperature and
pressure): 5
g/
cc
Melting point: 700°
C
Boiling point: 1,140°
C
Main
valence: +2
Ground state electron configuration: [
Rn]7s
2