When was the first noble gas discovered?

Argon was the first noble gas to be discovered, in 1894. Before that, chemists had no recognized group of chemically inert atmospheric gases. Argon’s discovery by Lord Rayleigh and William Ramsay helped reveal an entire family of elements that were hard to react with other substances. This was a major shift in periodic table chemistry because it showed that there were still unexplained gaps in the known elements.