Properties

Atomic Number	18
CAS Registry Number	7440-37-1
Chemical Symbol	Ar

History

The atomic number is 18 and the chemical symbol was originally just A but this symbol was changed to Ar in 1957. The name is derived from the Greek argos for lazy or inactive because it did not combine with other elements. It was discovered in 1895 by the Scottish chemist William Ramsay and the English physicist Robert John Strutt (Lord Rayleigh) in liquified atmospheric air. Rayleigh information. Thes initial interest was generated when he followed up on a problem posed by the English physicist Henry Cavendish in 1785 i.e. when oxygen and nitrogen were removed from air there was an unknown residual gas remaining.

Holden, Norman E., (2004). History of the origin of the chemical elements and their discoverers. National Nuclear Data Center. Retrieved from http://www.nndc.bnl.gov/content/elements.html