 About 90 atoms of flerovium have been observed : 58 were synthesized directly , and the rest were made from the radioactive decay of heavier elements . All of these flerovium atoms have been shown to have mass numbers from 284 to 289 . The most stable known flerovium isotope , flerovium @-@ 289 , has a half @-@ life of around 2 @.@ 6 seconds , but it is possible that this isotope may have a nuclear isomer with a longer half @-@ life of 66 seconds ; this would be one of the longest half @-@ lives of any isotope of a superheavy element . Flerovium is predicted to be near the centre of the theorized island of stability , and it is expected that heavier flerovium isotopes , especially the possibly doubly magic flerovium @-@ 298 , may have even longer half @-@ lives . 
