What is Promethium?
'''Promethium''' is a synthetic radioactive [[chemical]] [[Chemical element|element]] that has the symbol Pm on the [[periodic table]]. It has the atomic number 61 which means it has 61 [[proton]]s in its [[atom]]. It is the only synthetic element in the [[Lanthanide]] group as all its [[isotope]]s are [[radioactive decay|radioactive]]. Together with [[Technetium]], these are the only two radioactive elements below [[lead]]. Most Promethium is artificially produced. The longest-living isotope of promethium is <sup>145</sup>Pm, with a [[Half-life (element)|half-life]] of 17.7 years. == Uses == Promethium is used in the illuminated digits of some clocks, its [[Beta Radiation]] may be used to measure thickness. ==Related pages== * [[Periodic table]] * [[List of common elements]] {{Periodic Table}} {{chem-stub}} [[Category:Lanthanides]] [[Category:Synthetic elements]]