Inert gases such as helium, neon or argon are called inert gases. That means their atoms will never form stable molecules by bonding chemically with other different atoms. But in a discharge tube neon gas will glow. When electric voltage is applied to the electrodes fitted at the end of a glass tube containing inert gas under pressure, you can observe a light glow. This phenomenon was discovered in the first decade of 1900s by Georges Claude. In 1910, the historical day is 11 December; Claude displayed the first neon lamp to the public. He also discovered a blue glow when neon gas is replaced with argon gas. This invention has shown a way how to use this glow of inert gas neon for common purpose. In 1930 neon lighting was used in France for common illumination purpose. Later it has turned into eye-catching neon signs mainly used for advertisements. At first Georges Claude introduced neon gas signs to the United States.
In fact to speak the word neon is derived from the Greek ‘neos’, meaning ‘the new gas’. Neon gas is available in the atmosphere in the proportion of 1:65000 of air. William Ramsey and M.W. Travers were the two great scientists discovered neon gas in 1898. Neon gas can be extracted from the air by using liquefaction of air and fractional distillation techniques.
Basic sub atomic particle nature is to be known in order to understand why these gas discharges emit light. All know that every atom consists of electrons which are revolving in fixed orbits of variable energy. Due to the application of the voltage, the energy of the orbiting electron will increase thereby they jump from lower energy orbit to higher energy orbit. When this excited electron relaxes and comes to its initial position, then it emits energy in the form of light. This is the light which is having characteristic colors depends up on the energy difference between both the orbits.
You might have seen different colors of neon lights. In fact neon does not change colors when discharged in a sealed tube. Originally neon will give bright orange red color when it is properly heated in discharge tube. So to get different colors the gas has to be changed. If you are replacing neon with other elements such as mercury or combination of argon and phosphor you will get different colors. For getting blue color you have to use mercury. Similarly you can get bold yellow glow by using argon mixed with phosphor. Other gases such as carbon dioxide and helium provides white and gold glow respectively. Also many of these elements and gases can be intermixed in certain proportions to produce as many as different colors.