Starting from hydrogen ions ( protons ) , it principally produced deuterium , helium - 4 , and lithium .
Big Bang nucleosynthesis had a brief period during which it could operate , so only the very lightest elements were produced .
Starting from hydrogen ions ( protons ) , Big Bang principally produced deuterium , helium - 4 , and lithium .
Big Bang nucleosynthesis had a brief period during which it could operate , so only the very lightest elements were produced .