Helium-4
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| Helium-4 | |
|---|---|
| General | |
| Name, symbol | Helium-4, He-4,4He |
| Neutrons | 2 |
| Protons | 2 |
| Nuclide data | |
| Natural abundance | 99.999863% |
| Half-life | stable |
| Isotope mass | 4.002602 u |
Helium-4 (42He or 4He) is a non-radioactive and light isotope of helium. It is by far the most abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on earth. Its nucleus is the same as an alpha particle, consisting of two protons and two neutrons. The total spin of the nucleus is an integer so it is a boson. Alpha decay is a common decay mode for many radioactive isotopes. In fact, alpha decay of heavy elements is the source of most naturally occurring helium-4 on earth. Helium-4 is also produced by nuclear fusion in stars and during the Big Bang.
When helium-4 is cooled to below 2.17 kelvins (–271 °C), it becomes a superfluid, with properties that are very unlike those of an ordinary liquid. For example, if helium-4 is kept in an open vessel, a thin film will climb up the sides of the vessel and overflow. Another name for this property of helium is Rollin film. This strange behaviour is a result of the Clausius-Clapeyron relation and cannot be explained by the current model of classical mechanics nor by nuclear or electrical models; it is only understood as a quantum mechanical phenomenon.
| Lighter: Helium-3 |
Helium-4 is an isotope of helium |
Heavier: Helium-5 |
| Decay product of: Lithium-5 (p) Helium-5 (n) Beryllium-6 (2p) |
Decay chain of Helium-4 |
Decays to: Stable |
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