HELIUM

Helium (He) is a chemical element colorless, odorless, tasteless, non-toxic, virtually inert, monatomik, and is the first in a series of elements in the periodic table noble gases and atomic number 2. Its boiling and melting points are the lowest of the other elements and it exists only in the form of gas except in conditions of "extreme". Extreme conditions are also required to create a bit of helium compounds, which are all unstable at standard temperature and pressure. Helium has two stable isotopes of rare-called helium-3. Properties of liquid helium-4 varieties; helium I and helium II; important for researchers who study quantum mechanics (especially in the phenomenon of superfluidity) and for those looking for temperatures approaching absolute zero effect owned objects (such as superconductivity).

Helium is the second largest and lightest element in the universe and one of the elements that were created at the time of Big Bang nucleosynthesis. In the modern Universe almost all new helium is created in the process of nuclear fusion of hydrogen in the star. On Earth, these elements are created by radioactive decay of heavier elements (alpha particles are helium nuclei). After its creation, some of which is contained in the air (natural gas) in concentrations up to 7% volume. Purified helium from the air by low temperature separation process called fractional distillation.

In 1868, French astronomer Pierre Jules César Janssen first detected helium as a signature line of an unknown yellow spectral light from the eclipse of the sun. Since then a large helium content is found in many natural gas fields in the United States, which is the largest gas provider. Helium is used in cryogenic, deep-sea breathing systems, to cool superconducting magnets, the "helium dating", for the development of the balloon, to lift the aircraft and as a protective gas for industrial use (such as "arc welding") and the growth of silicon wafers). Inhaling a small amount of this gas will cause temporary changes in voice quality seseorang.Nama,
Chemical series: noble gases
Group, Period, Block: 18, 1, s
Appearance: colorless
Atomic mass: 4.002602 (2) g / mol
Electron configuration: 1s2
The number of electrons per skin: 2

Density (0 ° C, 101.325 kPa)
0.1786 g / L
Melting point (at 2.5 MPa) 0.95 K
(-272.2 ° C, -458.0 ° F)
4.22 K boiling point
(-268.93 ° C, -452.07 ° F)
Heat of fusion 0.0138 kJ / mol
Heat of vaporization 0.0829 kJ / mol
Heat capacity (25 ° C) 20.786 J / (mol ° K)