Lanthanum definition

lănthə-nəm
A soft, silvery-white, malleable, ductile, metallic rare-earth element, obtained chiefly from monazite and bastnaesite and used in glass manufacture and with other rare earths in carbon lights for movie and television studio lighting. Atomic number 57; atomic weight 138.91; melting point 920°C; boiling point 3,464°C; specific gravity 6.145 (at 25°C); valence 2, 3.
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A soft, malleable, silvery chemical element, one of the rare-earth elements and the first member of the lanthanide series: symbol, La; at. no. 57
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A soft, malleable, silvery-white metallic element of the lanthanide series. It is used to make glass for lenses and lights for movie and television studios. Atomic number 57; atomic weight 138.91; melting point 920°C; boiling point 3,469°C; specific gravity 5.98 to 6.186; valence 3.
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A metallic chemical element (symbol La) with an atomic number of 57.
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Origin of lanthanum

  • New Latin from Greek lanthanein to escape notice (from the finding of the element hidden in oxide of cerium)

    From American Heritage Dictionary of the English Language, 5th Edition

  • From Ancient Greek λανθάνω (lanthanō, “escape notice"), because it had gone long undetected in mineral ores.

    From Wiktionary