1、 As protective gas. (the chemical properties of rare gases are very inactive.)

When welding precision parts or active metals such as magnesium and aluminum, argon is often used as protective gas to isolate the air and prevent the metal from reacting with other substances at high temperature. The nuclear fuel cup of an atomic reactor will oxidize rapidly in the air, and it also needs to be machined under the protection of argon. The electric bulb is filled with argon to reduce the vaporization of tungsten wire and prevent the oxidation of tungsten wire, so as to prolong the service life of the bulb.


2、 As an electric light source. (when the rare gas is not powered on, it will emit different colors of light)

The first neon lamp in the world was filled with neon gas . The red light emitted by neon lamp has strong transmission force in the air and can pass through thick fog. Therefore, neon lights are often used in the light signs of airports, ports and waterway traffic lines. The lamp tube is filled with argon or helium and emits light blue or light red light respectively when powered on. A neon lamp with various colors can be made by filling the lamp tube with a mixture of helium, neon and argon. The fluorescent lamp commonly used in the door is made by filling a small amount of mercury and argon into the lamp tube and coating the inner wall with fluorescent substances (such as calcium halogen phosphate). When powered on, the discharge of mercury vapor in the tube produces ultraviolet light, which excites fluorescent substances and makes them emit visible light similar to sunlight. Therefore, it is called a fluorescent lamp.

Neon, krypton and xenon can also be used in laser technology.

3、 Medical treatment

Xenon has high ultraviolet radiation and can be used in medical technology. Xenon can dissolve in the fat of the cytoplasm, causing cell anesthesia and expansion, so as to temporarily stop the nerve endings and achieve the anesthetic effect. A mixture of 80% xenon and 20% oxygen has been tried as an anesthetic without side effects. Krypton and xenon isotopes are also used to measure cerebral blood flow.

4、 As artificial air

Helium and oxygen are mixed to produce artificial air for divers to breathe. Because in the deep sea with high pressure, breathing with ordinary air, there will be more nitrogen dissolved in the blood. When the diver rises from the deep sea and the body gradually recovers to normal pressure, the nitrogen dissolved in the blood will be released to form bubbles, which will block the microvessels and cause "air blockage". The solubility of helium in blood is much smaller than that of nitrogen. If the mixture of helium and oxygen (artificial air) is used to replace ordinary air, the staff sergeant phenomenon will not occur.


5、 Inflation

Helium is the lightest gas except hydrogen, which can neither burn nor support combustion. Hydrogen is flammable and explosive. Now helium has been used to fill balloons and gas boats instead of hydrogen.


6、 Low temperature

The boiling point of liquid helium is -269 ℃, which is the most difficult of all gases to liquefy. The ultra-low temperature near absolute zero (-273.15 ℃) can be obtained by using liquid nitrogen. Liquid helium with temperature above 2.2k is a normal liquid and has the general properties of general liquid. Liquid nitrogen with temperature below 2.2k is superfluid and has many abnormal properties. For example, it has superconductivity and low viscosity. Its viscosity becomes 1% of that of hydrogen, and this liquid helium can flow up the inner wall of the container and slowly down the outer wall of the container. This phenomenon is of great significance for the study and verification of quantum theory.