atomic number 61


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Noun1.atomic number 61 - a soft silvery metallic element of the rare earth group having no stable isotopeatomic number 61 - a soft silvery metallic element of the rare earth group having no stable isotope; was discovered in radioactive form as a fission product of uranium
metal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.
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Less well-known is the promethium, atomic number 61, in the paint on an old compass.