Why is helium generally absent from the Earth's atmosphere? Is it common anywhere else?
Helium is the second most common element in the universe after hydrogen as it the product of the fusion of hydrogen atoms. Helium is a very light element and is a noble gas. Due to its low mass, very stable electron configuration and inert behavior helium evaporates at a very low temperature. It is very difficult to convert gaseous helium to a liquid; the process requires temperatures close to absolute zero and very high temperatures.
It is theorized that during the formation of the Earth, the properties of helium caused it to escape from the cloud of matter that coalesced to form the Earth. This makes it a very rare element, almost absent in the atmosphere.
Helium is created on Earth due to radioactive decay. Alpha particles emitted when elements decay are nuclei of helium.