Facts

• Argon is a chemical element denoted by the symbol "Ar" on the periodic table. Its atomic number is 18 and it is a noble gas. According to the Chemistry Explained website, the element gets its name from the Greek name "argos," meaning slow or lazy, because of its nonreactive nature.
  
  

History

• Argon is the first inert gas to be discovered. In 1785, Henry Cavendish, an English physicist and chemist, performed an experiment in which he mixed air with oxygen and achieved some electrical discharges over a mixture of potassium hydroxide. During this process, he converted the nitrogen found in the air into potassium nitrate. When the oxygen excess was removed, a small amount of gas remained, but was considered an experimental error until about 100 years later. In 1894, Lord Rayleigh (John William Strutt) and William Ramsay studied the density of nitrogen and verified that the density of the nitrogen in the air was constantly larger than the density of the nitrogen present in compounds. They decided that this difference was too big to attribute to experimental errors, and concluded that there is a heavier inert substance found in the atmosphere, which came to be known as argon.
  
  

Characteristics

• At room temperature, argon is an odorless, colorless and tasteless monatomic (single atom) gas. Its melting point is -189.3 degrees C and its boiling point is -185.8 degrees C. It is the most abundant noble gas, present in the Earth's atmosphere at 0.941 percent. Its proportion in the air is constant, but a bit higher above sea level. Argon has the same solubility in water as oxygen, but is two-and-a-half times more soluble in water than nitrogen. As a result, there is more argon in liquid air than in the atmosphere.
  
  

Features

• Because argon is inert in most conditions (meaning that it does not form chemical bonds), it is often used in the research of non-bonding chemical interactions. Argon and other noble gases were considered to be fully chemically inert until 1962, when some compounds of the heavier noble gases were synthesized. Argon's first compound, argon fluorohydride, was formed only recently, in 2000, by scientists at the University of Helsinki.
  
  

Uses

• Argon is used in incandescent light bulbs because it protects the hot filament from oxidation and slows down the evaporation process. Argon is also used in fluorescent tubes (as the gas that makes them glow) and as insulating filler in double pane thermal windows.