Argon (Ar), krypton (Kr), neon (Ne) and xenon (Xe) belong to the group of noble gases, which are produced from air.
What they all share in common is that they occur only in very small quantities and react very little with other substances.
Argon is used as a shielding gas in many welding applications.
The group of noble gases includes helium, neon, argon, krypton and xenon along with radioactive radon and ununoctium (whereby the latter can only be generated synthetically). These gases are referred to as “noble” because – exactly like the noble metals gold, silver, platinum, etc – they form almost no chemical bonds under normal conditions. That’s why noble metals stay shiny and retain their “noble appearance” for a long time. By comparison, noble gases are even more “inert” and are therefore aptly named.
The noble gas most commonly found on Earth is argon (Ar). The air that surrounds us comprises barely one per cent argon. It is mainly used in the welding of aluminium alloys or special steels. In such cases it is used as a shielding gas, often in a mixture with other gases: argon shields the welding area from oxygen, which enhances the quality and durability of the welds.
The best-know application of helium (He) is probably free-floating party balloons. But helium also has a whole range of other important applications. For example, supercooled liquid helium is used in medicine as a coolant for the superconducting magnets of MRI scanners. Like argon, it is also used as a shielding gas, and it is also the most commonly used tracer gas in leak detection.
Krypton (Kr), xenon (Xe) and neon (Ne) are mainly used as fill gases and operating gases in lamps and lasers. The xenon headlights used in automotive construction are one well-known example. Not only are they significantly brighter than halogen headlights, but they also last longer. The gas which gives them their name, xenon, is required for a discharge process which produces the bright light. But halogen lamps are filled with noble gas mixtures, too. Xenon and neon are also the main components in the fill gas of plasma display screens.
In addition, krypton serves as a fill gas for double glazed windows: Filling the space between the panes with krypton provides significantly better insulation properties than when it is filled with air or argon.