Isotopes of platinum

Naturally occurring platinum (₇₈Pt) consists of five stableisotopes (Pt, Pt, Pt, Pt, Pt) and one long-lived (half-life 4.83×10 years) radioisotope (Pt). There are also 34 known synthetic radioisotopes ranging from Pt to Pt, and longest-lived of those is Pt with a half-life of 50 years. All the others have half-lives under two weeks, most under a day. There are numerous metastable states, of which the most stable are Pt and Pt with half-lives 4.33 and 4.010 days, decaying to their ground states.

Despite the obstacles to measurement with rare isotopes of rare elements, with a very slow decay, the Pt/Os system has been used in isotope geology, though not directly for dating.

All isotopes of platinum are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed. Platinum-195 is the most abundant isotope, making platinum one of the only three elements to have its most abundant isotope with an odd neutron number (the other two being beryllium and nitrogen); however, it is so only by a small margin, unlike the other two, and is more in the nature of a coincidence.