Helium is a colorless, odorless, tasteless, chemical element that exists as a nobel gas in all but extreme conditions. It is the second lightest element in the universe and also the second most common. However, it is relatively rare on Earth as our atmosphere contains only 0.00052% of the gas. There are only two stable isotopes of helium and the majority of helium on Earth is the more common of the two! Let’s find out how many isotopes of helium have been identified.
How many isotopes does helium have?
The two stable isotopes of helium are known as helium-3 and helium-4. The vast majority of helium in the universe is 4He and this is the same for our planet. In fact, 99.99986% of the helium found on Earth is 4He. The remaining 0.00014% is 3He, some of which was released into the atmosphere during nuclear weapons testing and via nuclear reactor releases (especially during an accident). Most of the 4He found in the atmosphere is a result of alpha decay of the heavy elements in the crust of the Earth.
Helium also has 7 unstable (radioactive) isotopes, which all have a very short half-life. These isotopes are known as helium-2 (also called diproton), and helium-5 through to helium-10. The longest lived of these isotopes is 6He with a half-life of 806.7 ms. The least stable is believed to be 5He or 2He.
Did you know?
Helium, in particular He4, makes up about 23% of the matter in the universe. Hydrogen makes up almost all of the rest of the matter in the universe!
Despite the fact that helium-3 is very rare it has a number of important uses. It is used in cryogenics, medical imaging and neutron detection. It is also being investigated for use in potential nuclear fusion.