Noun
English Wikipedia has an article on:helium-4Wikipedia
helium-4 (uncountable)
(physics) The normal isotope of helium, 2He, that has two neutrons
Also, the microscopic properties of helium-3 cause it to have a higher zero-point energy than helium-4. Source: Internet
Alpha particles are identical to a helium-4 nucleus (two protons and two neutrons), and travel at speeds in excess of 5% of the speed of light. Source: Internet
Assuming that sound waves are the most important excitations in helium-4 at low temperatures, he showed that helium-4 flowing past a wall would not spontaneously create excitations if the flow velocity was less than the sound velocity. Source: Internet
BBN did not convert all of the deuterium in the universe to helium-4 due to the expansion that cooled the universe and reduced the density and so, cut that conversion short before it could proceed any further. Source: Internet
Almost all neutrons that fused instead of decaying ended up combined into helium-4, due to the fact that helium-4 has the highest binding energy per nucleon among light elements. Source: Internet
At the same time it was clear that oxygen and carbon were the next two most common elements, and also that there was a general trend toward high abundance of the light elements, especially those composed of whole numbers of helium-4 nuclei. Source: Internet