Copernicium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesized in the laboratory, either by fusing two atoms or by observing the decay of heavier elements. Seven different isotopes have been reported with mass numbers 277 and 281–286, and one unconfirmed metastable isomer in Cn has been reported. Most of these decay predominantly through alpha decay, but some undergo spontaneous fission, and copernicium-283 may have an electron capture branch.