(From radium; called niton at first, L. nitens, shining) The element was discovered in1900 by Dorn, who called it radium emanation. In 1908 Ramsay and Gray, who named it niton,isolated the element and determined its density, finding it to be the heaviest known gas.It is essentially inert and occupies the last place in the zero group of gases in thePeriodic Table. Since 1923, it has been called radon.