Helium
Helium
Helium (pronounced /ˈhiːliəm/) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions.
Etymology
The term Helium comes from the Greek word Helios (Ἥλιος), meaning "Sun". It was named by Norman Lockyer and Edward Frankland, who discovered the element in the solar spectrum during an eclipse in 1868.
Properties and Uses
Helium is the second lightest and second most abundant element in the observable universe, being present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this figure in the Sun and in Jupiter. This is due to the very high nuclear binding energy (per nucleon) of helium-4, with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of both nuclear fusion and radioactive decay.
Helium is used in cryogenics, particularly in the cooling of superconducting magnets, with the main commercial application being in MRI scanners. Helium's other industrial uses—as a pressurizing and purge gas, as a protective atmosphere for arc welding and in processes such as growing crystals to make silicon wafers—account for half of the gas produced.
Related Terms
External links
- Medical encyclopedia article on Helium
- Wikipedia's article - Helium
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