An Etymological Dictionary of Astronomy and Astrophysics
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A radioactive metallic chemical element; symbol Ra. Atomic number 88; atomic weight 226.0254; melting point 700°C; boiling point 1,140°C. Discovered in 1898 by Marie Sklodowska Curie in an ore of pitchblende. In 1911 Curie and André Debierne successfully isolated radium by electrolysis.

N.L., from L. rad(ius)" ray, beam" → radius + -ium a noun suffix.