text: This postulate, however, does not apply to the universes most abundant and simplest element: hydrogen, with an atomic number of 1. This may be because, in its ionized form, a hydrogen atom becomes a single proton, of which it is theorized to have been one of the first major conglomerates of quarks during the initial second of the Universes inflation period, following the Big Bang. In this period, when inflation of the universe had brought it from an infinitesimal point to about the size of a modern galaxy, temperatures in the particle soup fell from over a trillion degrees to several million degrees.
  This period allowed for the fusion of single protons and deuterium nuclei to form helium and lithium nuclei but was too short for every H ion to be reconstituted into heavier elements. In this case, helium, atomic number 2, remains the even numbered counterpart to hydrogen. Thus, neutral hydrogen—or hydrogen paired with an electron, the only stable lepton—constituted the vast majority of the remaining unannihilated portions of matter following the conclusion of inflation.
  Another exception to the rule is beryllium which, despite an even atomic number (4), is rarer than adjacent elements (lithium and boron). This is because 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, each of which has two stable isotopes.