Even and odd atomic nuclei abundant isotopes of their element, the former only by a small margin, and the latter only because the expected beryllium-8 has lower binding energy than two alpha particles and therefore immediately alpha decays. Actinides with odd neutron number are generally fissile (with thermal neutrons), while those with even neutron number are generally not, though they are fissionable with fast neutrons. Only , and have odd neutron number and are the most naturally abundant isotope of their element. Even and odd atomic nuclei In nuclear physics, properties of a nucleus depend on evenness or oddness of its atomic number "Z", neutron
Even and odd atomic nuclei billion times the age of the universe. For example, the double beta emitter has a half-life of years. This makes for a larger number of stable even–even nuclides, up to three for some mass numbers, and up to seven for some atomic (proton) numbers. For example, the extreme stability of helium-4 due to a double pairing of 2 protons and 2 neutrons prevents "any" nuclides containing five or eight nucleons from existing for long enough to serve as platforms for the buildup of heavier elements via nuclear fusion in Big Bang nucleosynthesis; only in stars is there enough time for