noun
- a highly radioactive metallic chemical element that glows in the dark and was formerly used in luminous paints
Usage: chemistry
Examples
- Marie Curie discovered radium in 1898.
- Radium was once used to make watch dials glow in the dark.
- The element radium has the chemical symbol Ra.
- Workers who painted radium on clock faces suffered serious health problems.
- Radium is found naturally in uranium ores.
- The radioactive decay of radium produces radon gas.