Isotopes of platinum
Naturally occurring platinum consists of five stable isotopes and one long-lived radioisotope. There are also 34 known synthetic radioisotopes ranging from 165Pt to 204Pt, and longest-lived of those is 193Pt 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 193mPt and 195mPt 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 190Pt/186Os 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 Even and [odd atomic nuclei|odd neutron number] ; however, it is so only by a small margin, unlike the other two, and is more in the nature of a coincidence.