When flerovium-289 undergoes decay by emission of a single beta particle, it forms copernicium-289.
Flerovium-289 is an unstable isotope that can undergo beta decay, which is a type of radioactive decay in which a neutron inside the nucleus of an atom is converted into a proton, an electron and an electron antineutrino. This process increases the atomic number of the atom by one and leaves the mass number unchanged.