Periodic Table -> Helium


Helium Details

Helium Symbol: He

Helium Atomic Number: 2

Helium Atomic Weight: 4.0026

What is Helium?

Helium (atomic number 2, symbol He) is a non-toxic, tasteless, odorless, and colorless gas. Heading the noble group, it is an inert monoatomic gas, and its melting and boiling points are some of the lowest compared with other elements. Except in extreme conditions, helium exists as gas only. Helium is also the second most abundant and the lightest element, which is present in around 24 percent of the elemental mass. This makes over twelve times the combined mass of heavier elements. The abundance of helium is similar to this percentage in Jupiter and the Sun because of its high binding energy. Due to its binding energy, helium-4 is abundant, being the product of radioactive decay as well as nuclear fusion. Helium-4 accounts for most of the helium found in the universe. According to researchers, it was during the Big Bang when helium-4 was formed. The nuclear fusion of hydrogen which takes place in the stars accounts for the formation of new helium today.

Most of the helium on earth is produced as a result of radioactive decay. Some helium is present in the atmosphere, but its isolation and the subsequent separation of air is not cost-effective. It is cheaper and easier to isolate helium from some natural gases. In the United States, the concentration of helium was found to be as high as 7 percent in natural gases. Liquefaction and separations techniques are used to isolate it from these natural gases. This is not usually done in laboratory conditions, and the gas is kept in cylinders under pressure so that it is available commercially.

Helium has different applications, with mixtures of oxygen and helium being used as artificial air. It is also used for pressurizing liquid-fuel rockets and for filling balloons. Helium is heavier than hydrogen and safer to use in balloons because it does not burn. In the semi-conductor industry, the gas is used to create an inert atmosphere, which is suitable for growing germanium crystals and silicon. Helium is also employed in the production of zirconium and titanium because it is a high temperature gas. In gas chromatography, the element serves as a carrier gas. Liquid helium is used to generate superconductivity in some metals because of its low temperature.

In addition, helium is employed in impulse facilities and supersonic wind tunnels because of its calorically and thermally perfect nature, heat capacity ratio, high speed of sound, and inertness. In arc welding, the element is used as a shielding gas for materials that are weakened and contaminated by nitrogen or air at welding temperatures. Some shelding gases, which are inert in nature, are employed in tungsten arc welding. For materials with high heat conductivity, such as copper and aluminum, helium is used instead of argon. Leak detection is another industrial application of the gas. Helium diffusion through solids takes 3 times faster than that of air, and it is thus used to detect leaks in high-temperature containers, cryogenic tanks, and other high-vacuum equipment. To test an object, it is put in a chamber and then filled with helium after being evacuated. Among its other uses, helium is used in rocketry. It serves as an ullage medium where oxidizers and fuel are displaced as to condense oxygen and hydrogen and produce rocket fuel. Prior to launch, helium is employed to purge oxidizer and fuel from the ground support equipment.

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