|Atomic mass||20.179 amu|
Neon was discovered in 1898, just weeks later that krypton was discovered. Using the same techniques to discover krypton, atmospheric gases were cooled sufficiently such that a cold mix of gases and liquids were collected. Then helium and argon were drawn off. But this time, investigators looked closely at the helium and argon fraction. They improved on the sensitivity of their fractional distillation procedure and found the new gas. When the gas was subjected to an electric arc, it emitted a brilliant red glow that we now recognize as characteristic of neon signs. This took place in June 1898. In less than a month, they would discover xenon.
Liquefaction of air is a large-scale commercial process today. This process provides the primary source of liquid oxygen (O2 (g) liquefies at -118°C), and nitrogen ( N2 (g) liquefies at -150°C). At -150°C, neon remains in the gas phase (boiling point of neon is-229°C). In fact, at this temperature, the gas phase is comprised of roughly 75% neon, 24% helium, and a trace of hydrogen. By passing the cool gas through activated charcoal helium and hydrogen can be removed. Commercial neon is thus produced as a secondary product at liquid N2/liquid O2 plants.
The most popularly known commercial application is neon signs for advertising. A minute amount of neon is confined in a glass tube that is fitted with an electrical connection at each end. When a sufficiently high voltage is applied to the electrodes, the gas glows with an even intensity throughout the length of the tube. Neon tubes can be bent and twisted into an infinite variety of meaningful and interesting shapes without degrading the quality of the light. Shown above is the familiar red-orange glow discharge of neon.