Helium
Symbol: He
Atomic number: 2
Average atomic mass: 4.003
Properties/ Characteristics
Helium is colorless, odorless, tasteless, and non-toxic. It is a noble gas, and sometimes a solid in extreme conditions. Unlike any other element, helium will fail to solidify and remain a liquid down to absolute zero at normal pressures. Its melting point is about -458 degrees F. The boiling points is about -452.07 degrees F.
Helium is the second most abundant element in the known Universe after hydrogen and constitutes 23% of the elemental mass of the universe. It is concentrated in stars, where it is formed from hydrogen by the nuclear fusion of the proton-proton chain reaction and CNO cycle.
History and Discovery
Helium was found by Pierre Janneson, Norman Lockyer, and Edward Frankland in 1868. The element was first spotted as a yellow line in the spectrum of the chromosphere of the Sun during a solar eclipse and was though at first to be sodium.
On 26 March 1895 British chemist William Ramsay isolated helium on Earth by treating the mineral cleveite with mineral acids.
Uses
Helium can be used in party balloons and airships such a blimps. Liquid helium can be used as a cryogenic material, and is used to cool certain metals to produce superconductivity. Helium has high thermal conductivity, neutron transparency, and does not form radioactive isotopes under reactor conditions, so it is used as a coolant in some nuclear reactors. The age of rocks and minerals that contain uranium and thorium can be discovered by measuring the level of helium with a process known as helium dating.
The voice of a person who has inhaled helium temporarily sounds high-pitched. This is because the speed of sound in helium is nearly three times the speed of sound in air, however, this can be dangerous if done to excess since helium is a simple asphyxiant, thus it displaces oxygen needed for normal respiration. Death by asphyxiation will result within minutes if pure helium is breathed continuously.
This information was found at http://en.wikipedia.org/wiki/Helium
