lanthanum
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θə< Neo-Latin (1841), equivalent to lanthan- (< Greek lanthánein to escape notice; referring to its position on the periodic table) + -um, variant of -ium -ium
Based on the Random House Dictionary, © Random House, Inc. 2013.
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lanthanum (ˈlænθənəm) ![[Click for IPA pronunciation guide]](http://static.sfdict.com/dictstatic/g/d/dictionary_questionbutton_default.gif) | |
| —n | |
| 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] | |
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| a screen or mat covered with a dark material for shielding a camera lens from excess light or glare. |
| a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes. |
lanthanum
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lanthanum lan·tha·num (lān'thə-nəm)
n.
Symbol La
A soft malleable metallic rare-earth element used in glass manufacture. Atomic number 57; atomic weight 138.91; melting point 920°C; boiling point 3,455°C; specific gravity 6.145 (at 25°C); valence 3.
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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| lanthanum (lān'thə-nəm) Pronunciation Key
Symbol La 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. See Periodic Table. |
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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lanthanum
((La), chemical element, rare-earth metal of transition Group IIIb of the periodic table, prototype of the lanthanoid series of elements. Lanthanum is a ductile and malleable, silvery-white metal, soft enough to be cut with a knife. The element was discovered as the oxide (lanthana) in 1839 by Carl Gustaf Mosander, who distinguished it from cerium oxide (ceria). Its name is derived from the Greek lanthanein, meaning "to be concealed," indicating that it is difficult to isolate
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