Here's a breakdown:
* 1868: While studying the spectrum of the sun, Pierre Janssen and Norman Lockyer observed a yellow line that didn't match any known element. They named this element helium.
* 1894: Ramsay, along with Lord Rayleigh, investigated the discrepancy in density between nitrogen extracted from the air and nitrogen obtained from chemical compounds. Their findings led them to discover argon, the first inert gas to be isolated.
* 1895-1898: Ramsay, with the help of Morris Travers, went on to discover neon, krypton, and xenon by fractionally distilling liquid air.
* 1900: Radon, the final inert gas, was discovered by Friedrich Ernst Dorn as a radioactive decay product of radium.
Therefore, while other scientists made important contributions, William Ramsay is widely recognized for discovering and characterizing the inert gases, which are now known as noble gases.
