Discovered : 1899 by Lord Rayleigh and Sir William Ramsay Origin : From the Greek ‘argos’ meaning inactive. Description : The third most abundant gas making up one percent of the atmosphere. The quantity has increased since the Earth was formed because radioactive potassium turns into argon as it decays. Argon is a colourless, odourless gas that is totally inert to other substances, and for this reason it is ideal in tube lights. Image : Welding - Argon provides an inert atmosphere in which welded metals will not burn.