High Quality Content by WIKIPEDIA articles! Promethium (Pm) has no stable isotopes, and does not exist in nature, except in trace quantities as a product of spontaneous fission and alpha decay of 151Eu. It is a synthetic element, first produced in 1945. Thirty-eight radioisotopes have been characterized, with the most stable being 145Pm with a half-life of 17.7 years, 146Pm with a half-life of 5.53 years, and 147Pm with a half-life of 2.6234 years. All of the remaining radioactive isotopes have half-lives that are less than 365 days, and the majority of these have half-lives that are less than 30 seconds. This element also has 18 meta states with the most stable being 148mPm (T? 41.29 days), 152m2Pm (T? 13.8 minutes) and 152mPm (T? 7.52 minutes). Данное издание представляет собой компиляцию сведений, находящихся в свободном доступе в среде Интернет в целом, и в информационном сетевом ресурсе "Википедия" в частности. Собранная по частотным запросам указанной тематики, данная компиляция...