right|thumb|400px|the expected location of the island of stability  in nuclear physics, the island of stability is a set of predicted, but as-yet undiscovered, heavier isotopes of transuranium elements which are theorized to be much more stable than some of those closer in atomic number to uranium. specifically, they are expected to have radioactive decay half-lives of minutes or days, with "some optimists" expecting half-lives of millions of years. klaus blaum expects the island of stability to occur in the region near 300ubn.quoting: âwe expect [the island of stability] at around element 120,â says blaum, âand to be more precise, in a nucleus with around 180 neutrons.â ==theory and origin==  the possibility of an "island of stability" was first proposed by glenn t. seaborg in the late 1960s. the hypothesis is based upon the nuclear shell model, which implies that the atomic nucleus is built up in "shells" in a manner similar to the structure of the much larger electron shells in atoms. in both cases, shells are just groups of quantum energy levels that are relatively close to each other. energy levels from quantum states in two different shells will be separated by a relatively large energy gap. so when the number of neutrons and protons completely fills the energy levels of a given shell in the nucleus, the binding energy per nucleon will reach a local maximum and thus that particular configuration will have a longer lifetime than nearby isotopes that do not possess filled shells.{{cite web| title = shell model of nucleus | work = hyperphysics | publisher = department of physics and astronomy, georgia state university | url = http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/shell.htm
Isotopes Periodic_table Radioactivity