Helium

Helium is a chemical element with atomic number 2 and an atomic mass of 4.002602, which is the symbol. It 'a colorless, odorless, tasteless, nontoxic, monatomic inert gas, which leads to the group of noble gases in the periodic table. Its boiling and melting points are the lowest among the elements, and only exists as a gas except in extreme conditions. In addition to hydrogen, is the second most abundant element in the universe, and accounts for 24% of the primary mass of our galaxy.

Spectral signature of an unknown yellow line in the sun was observed for the first time a solar eclipse in 1868 by French astronomer Jules Janssen. Janssen is in common with the discovery of the element with Norman Lockyer, who has observed the same eclipse and was the first to propose that the line with a new element called helium credited. In 1903, large reserves of helium in natural gas fields in some parts of the United States, has been by far the largest gas supplier.

Helium is used in cryogenics (I use the largest single investment, which is about one quarter of production), in particular the cooling of superconducting magnets, with the main application in the commercial MRI scanner. Other industrial applications such as pressure helium gas purge and protective atmosphere for processes such as arc welding and crystal growth of silicon wafers to make half of its use. Economically, the small, like gas balloons and airships lifting are popularly known [2]. Like all gases with different densities of air, inhalation of a small amount of helium temporarily changes the timbre and quality of the human voice. In scientific research, the behavior of two liquid phases of the study helium-4, helium I and helium II, researchers in quantum mechanics (in particular the phenomenon of superfluidity) and the importance of the effects that temperatures near absolute zero on matter (such as superconductivity).

Helium is the second lightest element and is the second most common in the observable universe, in which the universe, in masses more than 12 times higher than that of heavier elements combined. Its abundance is also similar to our Sun and Jupiter. This is due to the high bond energy (per nucleon) of helium-4 in relation to the following three elements after helium (lithium, beryllium and boron). This energy helium-4 is also binding for the community both as a product of nuclear fusion and radioactive decay. Most helium in the universe is helium-4, and is likely to be created during the Big Bang. Some new helium is created as a result of nuclear fusion of hydrogen in stars more than 0.5 solar masses.

On Earth, the lightness of helium causes the evaporation of clouds of gas and dust from which planets condensed, is relatively rare-0, 00 052% by volume in the atmosphere. Most terrestrial helium is present through the natural radioactive decay of heavy radioactive elements (uranium and thorium), such as alpha particles emitted by the decay as created by the nuclei of helium-4. This radiogenic helium is trapped with natural gas in concentrations of up to 7% by volume, of which he won in the trade called a process of cryogenic separation by fractional distillation.