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.
Isotopes of titanium
Titanium-44 is a radioactive isotope of titanium that undergoes electron capture to an excited state of scandium-44 with a half-life of 60 years, before the ground state of Sc and ultimately Ca are populated. Because titanium-44 can only undergo electron capture, its half-life increases with ionization and it becomes stable in its fully ionized state.