The first atom (the electron is bound to it) are theoretically created 380,000 years after the Big Bang, when the expanding universe is cool enough to allow the electrons bound to nuclei.
Since then, the nucleus began to join in the stars through nuclear fusion processes, and produce elements heavier until the iron.
Isotopes such as lithium-6 is produced in space through cosmic ray spalasi. This occurs when a high-energy proton nucleus pound, causing a large number of nucleon scattering.
Elements heavier than iron are produced in a supernova r process and in AGB stars through the process of s. Both involve the capture of neutrons by atomic nuclei. Elements such as lead mostly formed through the radioactive decay of other elements heavier.
