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Also known as Pm, element 61, ₆₁Pm
Promethium is a chemical element; it has symbol Pm and atomic number 61. All of its isotopes are radioactive; it is extremely rare, with only about 500–600 grams naturally occurring in the Earth's crust at any given time. Promethium is one of the only two radioactive elements that are both preceded and succeeded in the periodic table by elements with stable forms, the other being technetium. Chemically, promethium is a lanthanide. Promethium shows only one stable oxidation state of +3.
Promethium is a rare radioactive element (symbol Pm, atomic number 61) that is extremely scarce in nature, with only about 500–600 grams existing in Earth's crust at any given time. It's notable for being one of only two radioactive elements sandwiched between stable elements on the periodic table, and it belongs to the lanthanide family of elements.
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Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).