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n. Symbol La
A soft, silvery-white, malleable, ductile element of the lanthanide series, obtained chiefly from the minerals monazite and bastnaesite and used in glass manufacture and with other rare-earth elements 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. See Periodic Table.
[New Latin, from Greek lanthanein, to escape notice (from the finding of the element hidden in oxide of cerium).]
(Elements & Compounds) a silvery-white ductile metallic element of the lanthanide series, occurring principally in bastnaesite and monazite: used in pyrophoric alloys, electronic devices, and in glass manufacture. Symbol: La; atomic no: 57; atomic wt: 138.9055; valency: 3; relative density: 6.145; melting pt: 918°C; boiling pt: 3464°C
[C19: New Latin, from Greek lanthanein to lie unseen]
lan•tha•num(ˈlæn θə nəm)
a rare-earth, trivalent, metallic element, allied to aluminum, found in certain minerals, as monazite. Symbol: La; at. wt.: 138.91; at. no.: 57; sp. gr.: 6.15 at 20°C.
[< New Latin (1841) < Greek lanthán(ein) to escape notice + New Latin -um, for -ium -ium2]
Symbol La A soft, easily shaped, 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. See Periodic Table.
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|Noun||1.||lanthanum - a white soft metallic element that tarnishes readily; occurs in rare earth minerals and is usually classified as a rare earth|