most of the universe's lithium, beryllium, and boron are made by cosmic ray spallation, not ordinary stellar nucleosynthesis, and beryllium has only one stable isotope, causing it to lag in abundance with regard to its neighbors, which both have two stable isotopes. Relationship to fusion The pattern arises after the runaway fusion in a dying massive star occurs, in which a given mass of the various even and odd numbered elements are formed by a slightly greater mass of the elements hydrogen and helium. The newly formed elements are ejected in the explosion and eventually join the rest of the galaxy's interstellar medium. When fusion occurs with larger and larger nuclei, the energy input becomes increasingly larger and the energy output becomes increasingly smaller; the point at which these two potentials meet on the periodic table of elements is somewhere around the elements iron, atomic number 26, and nickel, atomic number 28. Fusion of heavier elements than this does not release energy, and so the probability of finding discrepancies in the Oddo–Harkins rule becomes lower. See also References Nuclear chemistry