 
Colourless and odourless, neon (Ne) is a noble gas at room temperature that will not react with any other substance. It is an element that is number 10 in the periodic table. Neon is the fifth most abundant element in the universe. However, it is present in the Earth's atmosphere at a concentration of just 18 parts per million. It is obtained by processing liquid air; processing 89,000 kilograms of liquid air produces just 1 kilogram of neon. 
The largest use of neon has always been in making neon signs for advertising. In a vacuum tube neon glows a reddish orange colour. Only red signs actually contain pure neon. Others contain different gases to give different colours. Many neon signs were made from glass containing lead. Health concerns over the use of lead contributed to the decline of neon signage in favor of safer options.The biggest difference between older neon signs and modern ones is that most modern 'neon' signs do not actually use neon – instead they simply use coloured LEDs that help to simulate the colours produced by traditional signs. While still used in advertising, modern neon-style signs are now often used in an artistic manner. Many are used to create eye-catching images rather than text, to help set a mood. Neon is also used in high-voltage equipment, lightning arresters, diving equipment and lasers. Liquid neon is an important cryogenic refrigerant. It has over 40 times more refrigerating capacity per unit volume than liquid helium, and more than 3 times that of liquid hydrogen. |