Promethium, originally prometheum, is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium. Chemically, promethium is a lanthanide, which forms salts when combined with other elements. Promethium shows only one stable oxidation state of +3; however, a few +2 compounds may exist.
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Some articles on promethium:
... Promethium-147 can emit X-rays during its beta decay, which are dangerous for all lifeforms ... Interactions with tiny quantities of promethium-147 are not hazardous if certain precautions are observed ... It is not known what human organs are affected by interaction with promethium a possible candidate is the bone tissues ...