Helium: the essentials
Helium is one of the so-called noble gases. Helium gas is an unreactive, colourless, and odourless monoatomic gas. Helium is available in pressurised tanks.
Helium is the second most abundant element in the universe after hydrogen. α-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!).
Helium is present in the atmosphere at about 0.0005% (1 part in 200000) by volume and is an important component within hydrocarbon gases in the USA. Its origin in these gases is traced to the decay of radioactive elements in rocks.
Emma's first birthday balloon is filled with helium and so rises in air.
Helium: historical information
A French astronomer, Pierre-Jules-César Janssen (1824-1907), first obtained evidence for the existence of helium during the solar eclipse of 1868 in India when he detected a new yellow line (587.49 nm) in the solar spectrum very close to the yellow sodium D-line. It was not possible to produce this line in the laboratory. Sir Norman Lockyer (1836-1920), an English astronomer, recognised that no known element at that time gave this line and named the element helium for the sun. For many years helium was regarded as an element that might exist on the sun although it was unknown on the Earth. Spectroscopists at the time doubted the results concerning helium. However the claims initiated a search for the new element on planet earth. In 1895, Sir William Ramsay discovered helium after treating cleveite, a uranium mineral, with mineral acids. Ramsey sent samples of the gas to Sir William Crookes and Sir Norman Lockyer who identified helium. It was discovered independently in clevite by Cleve and Langley at about the same time. Lockyer and Professor Edward Frankland suggested the name helium.
Helium around us Read more »
Helium has no biological role.
Helium is present in the atmosphere at about 0.0005% (1 part in 200000) by volume and is an important component within hydrocarbon gases in the USA. Its origin in these gases is traced to the decay of radioactive elements in rocks. Some minerals contain occluded helium and this can be liberated by heating. Some rocks consist of minerals which contain uranium and potassium. These decay to helium and argon and analysis of these gases can be used to determine the age of the rock. The bulk of the western world's supply is obtained from wells in the USA.
Helium is the second most abundant element in the universe. It is very common in the hotter stars. It is an important component in the proton-proton reaction and the carbon cycle in stars.
|Location||ppb by weight||ppb by atoms||Links|
|Human||(no data) ppb by weight||(no data) atoms relative to C = 1000000|
Physical properties Read more »
Heat properties Read more »
- Melting point: 0.95 [‑272.2 °C (‑458 °F)] K
- Boiling point: 4.22 [‑268.93 °C (‑452.07 °F)] K
- Enthalpy of fusion: |203| kJ mol-1
Crystal structure Read more »
The solid state structure of helium is: ccp (cubic close-packed).
Helium: orbital properties Read more »
Helium atoms have 2 electrons and the shell structure is 2. The ground state electronic configuration of neutral Helium is 1s2 and the term symbol of Helium is 1S0.
- Pauling electronegativity: (no data) (Pauling units)
- First ionisation energy: 2372.3 kJ mol‑1
- Second ionisation energy: 5250.5 kJ mol‑1
Isolation: 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.
Helium isotopes Read more »
Helium has two isotopes but it consists almost entirely of He-4 with natural He only containing just over 0.0001% of He-3. Thousands of liters of He-3 are used annually in cryogenic applications and He-3 is also used as a neutron counter in nuclear application. He-3 is also applied in magnetic resonance imaging.
|3He||3.016 029 309 7(9)||0.000137 (3)||1/2||-2.127624|
|4He||4.002 603 2497(10)||99.999863 (3)||0||0|