Argon

Argon makes up almost 1% of the air, far more than any other noble gas, because it is constantly produced by the radioactive decay of potassium in rocks. Its name comes from the Greek for lazy, since it reacts with nothing. Lord Rayleigh and William Ramsay discovered it in 1894 after noticing that nitrogen taken from air was slightly heavier than nitrogen made chemically.

Argon is collected when air is liquefied and separated. Because it is inert and cheap, it shields hot metal from air during welding and steelmaking, fills incandescent bulbs and double-glazed windows, and protects the growing silicon ingot as it is pulled from the melt.