Helium was the first of the noble gases to be discovered, and is unusual in that it was discerned as a yellow line in the solar spectrum before it was found on earth. Pierre Janssen and Joseph Norman Lockyer noted the existence of the new element during a solar eclipse in 1868. Its terrestrial presence was confirmed in 1895 by William Ramsay.
Ramsay was the first to suggest that the noble gas group might exist. Mendeleyev, in his famous work on the periodic table, had not considered the idea of an entirely new group, but during the 1890s Ramsay succeeded, by the fractional distillation of liquid air, in isolating argon, krypton, neon and xenon, none of which could fit into the existing version of the periodic table. The new group became known as the 'inert gases' because of its members' apparent inability to form compounds, but as some of the gases are now known to be capable of reaction, the name 'noble gases' has been deemed more appropriate.
Radon, a radioactive element, was first isolated by Ernest Rutherford in 1902.
