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rubidium

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ru⋅bid⋅i⋅um

[roo-bid-ee-uhm]
–noun Chemistry.
a silver-white, metallic, active element resembling potassium, used in photoelectric cells and radio vacuum tubes. Symbol: Rb; atomic weight: 85.47; atomic number: 37; specific gravity: 1.53 at 20°C.

Origin:
1860–65; < NL, equiv. to L rūbid(us) red (in allusion to the two red lines in its spectrum) + -ium -ium


ru⋅bid⋅ic, adjective
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Based on the Random House Dictionary, © Random House, Inc. 2009.
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ru·bid·i·um   (rōō-bĭd'ē-əm)   
n.   Symbol Rb
A soft silvery-white metallic element of the alkali group that ignites spontaneously in air and reacts violently with water, used in photocells and in the manufacture of vacuum tubes. Atomic number 37; atomic weight 85.47; melting point 38.89°C; boiling point 688°C; specific gravity (solid) 1.532; valence 1, 2, 3, 4. See Table at element.

[From Latin rūbidus, red; see reudh- in Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Medical Dictionary

Main Entry: ru·bid·i·um
Pronunciation: rü-'bid-E-&m
Function: noun
: a soft silvery metallic element that decomposes water withviolence and bursts into flame spontaneously in air —symbol Rb; —see ELEMENT table
Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.
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Medical Dictionary

rubidium ru·bid·i·um (r&oomacr;-bĭd'ē-əm)
n.
Symbol Rb
A soft metallic element of the alkali group. Atomic number 37; atomic weight 85.47; melting point 39.31°C; boiling point 688°C; specific gravity (solid) 1.532; valence 1, 2, 3, 4.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Encyclopedia

rubidium

chemicalchemical element of Group 1 (also called Group Ia) in the periodic table, the alkali metal group. Rubidium is the second most reactive metal and is very soft, with a silvery-white lustre. A brief treatment of rubidium follows. For full treatment, see alkali metal.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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