Led to the conclusion by different paths and, at first, without working together, both Lord Rayleigh and Ramsay succeeded in proving that there must exist a previously unknown gas in the atmosphere. They subsequently worked in their separate laboratories on this problem but communicated the results of their labours almost daily. At the meeting of the British Association in August 1894, they announced the discovery of argon.

William Ramsay, Nobel Lecture Nobel Lecture, December 12, 1904

"In September, 1898, the discovery of another gas was announced; it was separated from krypton by fractionation, and possessed a still higher boiling point. We named it 'xenon' or the 'stranger'".

While seeking sources of argon in the mineral kingdom, Ramsay discovered helium in 1895. Then guided by theoretical considerations founded on Mendeleev's periodic system, he methodically sought the missing links in the new group of elements and in 1898 found neon, krypton, and xenon.

Ramsay, with Frederick Soddy also detected helium in the emanations of radium in 1903.

Ramsay received the Nobel Prize in Chemistry in 1904, "in recognition of his services in the discovery of the inert gaseous elements in air", along with Lord Rayleigh who received the Nobel Prize in Physics in the same year for the discovery of argon.