Uranium
In nature, uranium is found as uranium-238 (99.2739–99.2752%), uranium-235 (0.7198–0.7202%), and a very small amount of uranium-234 (0.0050–0.0059%). Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years, making them useful in dating the age of the Earth.
Nihonium
All nihonium isotopes are unstable and radioactive; the heavier nihonium isotopes are more stable than the lighter ones, as they are closer to the centre of the island. The most stable known nihonium isotope, Nh, is also the heaviest; it has a half-life of 8 seconds. The isotope Nh, as well as the unconfirmed Nh and Nh, have also been reported to have half-lives of over a second. The isotopes Nh and Nh have half-lives of 1 and 0.1 seconds respectively. The remaining two isotopes have half-lives between 0.1 and 100 milliseconds: Nh has a half-life of 70 milliseconds, and Nh, the lightest known nihonium isotope, is also the shortest-lived, with a half-life of 1.4 milliseconds. This rapid increase in the half-lives near the closed neutron shell at "N" = 184 is seen in roentgenium, copernicium, and nihonium (elements 111 through 113), where each extra neutron so far multiplies the half-life by a factor of 5 to 20.