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below: |Nucleus · Nucleons (p, n) · Nuclear force · Nuclear
reaction| In geochemistry and geonuclear physics, primordial
nuclides', also known as primordial isotopes, are nuclides found
on the Earth that have existed in their current form since
before Earth was formed. Primordial nuclides are residues from
the Big Bang, from cosmogenic sources, and from ancient
supernova explosions which occurred before the formation of the
solar system. They are the stable nuclides plus the long-lived
fraction of radionuclides surviving in the primordial solar
nebula through planet accretion until the present. Only 289 such
nuclides are known. All of the known 254 stable nuclides