Helium [He] (CAS-ID: 7440-59-7) locate me
An: 2 N: 2 Am: 4.002602
Group No: 18 Group Name: Noble gas
Block: p-block Period: 1
State: gas at 298 K
Colour: colourless Classification: Non-metallic
Boiling Point: 4.215K (-268.93'C)
Melting Point: 0.95K (-272.2'C)
Density: 0.1786g/l
Availability: There is very little helium on earth as nearly all present during and immediately after the earth's formation has long since been lost as it is so light. Just about all the helium remaining on the planet is the result of radioactive decay. While there is some helium in the atmosphere, currently its isolation from that source by liquefaction and separation of air is not normally economic. This is bacause it is easier, and cheaper, to isolate the gas from certain natural gases. Concentrations of helium in natural gas in the USA are as high as 7% and other good sources include natural gas from some sources in Poland. It is isolable from these gases by liquefaction and separation of from the natural gas. This would not normally be carried out in the laboratory and helium is available commercially in cylinders under pressure.
Shell Structure diagrams | Atomic Radius diagram
Isotopes

Discovery Information
Who: Sir William Ramsey , Nils Langet, P T Cleve
When: 1895
Where: Scotland/Sweden
Name Origin
Greek: helios (sun).
Sources
Found in natural gas deposits and in the air (5 parts per billion) Constantly lost to space; replenished by radioactive decay (alpha particles). Helium is the second most abundant element in the universe by mass (25%). Most of the helium supplied around the world comes from the area around Amarillo, Texas.
Uses
Used in balloons, deep sea diving and welding. Also used in very low temperature research and nuclear power plant coolant. Future possible uses include use as coolant for nuclear fusion power plants and in superconducting electric systems.
Notes
Helium has the lowest melting and boiling point of any element. Liquid Helium is called a "quantum fluid" as it displays atomic properties on a macroscopic scale. The viscosity of liquid helium is 25 micropoises (water has a viscosity of 10,000 micropoises). As helium is cooled below its transition point, it has an unusual property of superfluidity with a viscosity approaching zero micropoises. In addition, liquid helium has extremely high thermal conductivity.
Helium is the second most abundant and second lightest element in the periodic table. It is also the least reactive of all the group 18 ( noble gases ) elements.
One cubic metre of helium with lift 1kg. Helium is the preferred choice for airships as although it is more expensive it is not flammable and has 92% the lifting power of hydrogen.
The voice of a person who has inhaled helium temporarily sounds high-pitched, resembling those of the cartoon characters "Alvin and the Chipmunks". This is because the speed of sound in helium is nearly three times that in air.
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