|Name: helium||Group number: 18|
|Symbol: He||Group name: Noble gas|
|Atomic number: 2||Period number: 1|
|Atomic weight: 4.002602 (2) g r||Block: p-block|
|CAS Registry ID: 7440-59-7||Voice: |
|Standard state: gas at 298 K||Colour: colourless|
|Classification: Non-metallic||Availability: |
Emma"s first birthday balloon is filled with helium and so rises in air.
Helium is one of the so-called noble gases. Helium gas is unreactive, colourless, and odourless. Helium is available in pressurised tanks.
Elemental helium is a colourless odourless monoatomic gas. Helium is the second most abundant element in the universe after hydrogen. a particles are doubly ionised helium atoms, He2+.
Helium is used in lighter than air balloons and while heavier than hydrogen, is far safer since helium does not burn. Speaking after breathing an atmosphere rich in helium results in a squeaky voice (don"t try it!).
IsolationHere is a brief summary of the isolation of helium.
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.