What Is Neon?

When we walk down the main street of a city at night, we see all sorts of coloured lights on stores and advertising signs. We think of them as neon lights.

But the fact is that not all of them are lights made by glowing neon gas. Other gases, such as helium, argon, krypton, and xenon, are also used in lights. Each gas gives out a different-coloured light when electricity is sent through it,

The colour of the light given out will vary, depending on such things as the temperature, pressure, and electric voltage. Neon gives out a red-orange light; argon gives out a reddish-blue light; the light from helium is white, yellow, or sometimes violet; from krypton it is yellow, green, or pale violet; and from xenon it is either blue or blue-green.

By passing electricity through neon gas, the atoms are made to give off light. What happens is that the energy of the electric cur­rent knocks electrons off some of the atoms of neon. When these electrons rejoin the neon atoms, energy in the form of light is given off.

All the gases we have mentioned here form a family of elements called the noble gases. Sometimes they are called rare gases because they are fairly scarce. All of these gases are relatively inactive chem­ically. This means they do not burn, and they form no chemical com­pounds under normal conditions.

The chief source of these gases is ordinary air (except for helium, which is obtained from natural gas). The gases are mixed together in the air with oxygen, nitrogen, carbon dioxide, and other substances.

To get the noble gases, the air is separated into its elements, and the gases are removed one at a time. This is done by chilling air to a very low temperature so that it turns into a liquid. The liquid air is piped into tall towers and heated.

As each gas reaches its boiling point, it boils off from the liquid air as a gas.