|a gadget; dingus; thingumbob.|
|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
|—the chemical symbol for|
|2.||astronomy right ascension|
|3.||(in Britain) Royal Academician or Academy|
|4.||(in Britain) Royal Artillery|
|5.||Argentina (international car registration)|
|[(sense 5) from República Argentina]|
The symbol for the element radium.
The symbol for radium.
|radium (rā'dē-əm) Pronunciation Key
A rare, bright-white, highly radioactive element of the alkaline-earth group. It occurs naturally in very small amounts in ores and minerals containing uranium, and it is naturally luminescent. Radium is used as a source of radon gas for the treatment of disease and as a neutron source for scientific research. Its most stable isotope is Ra 226 with a half-life of 1,622 years. Atomic number 88; melting point 700°C; boiling point 1,737°C; valence 2. See Periodic Table.