Noble \No"ble\, a. [Compar. Nobler; superl. Noblest.] [F.
noble, fr. L. nobilis that can be or is known, well known,
famous, highborn, noble, fr. noscere to know. See know.]
1. Possessing eminence, elevation, dignity, etc.; above
whatever is low, mean, degrading, or dishonorable;
magnanimous; as, a noble nature or action; a noble heart.
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Statues, with winding ivy crowned, belong
To nobler poets for a nobler song. --Dryden.
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2. Grand; stately; magnificent; splendid; as, a noble
edifice.
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3. Of exalted rank; of or pertaining to the nobility;
distinguished from the masses by birth, station, or title;
highborn; as, noble blood; a noble personage.
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Note: Noble is used in the formation of self-explaining
compounds; as, noble-born, noble-hearted, noble-minded.
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Noble gas (Chem.), a gaseous element belonging to group
VIII of the periodic table of elements, not combining with
other elements under normal reaction conditions;
specifically, helium, neon, argon, krypton,
xenon, or radon; also called inert gas.
Noble metals (Chem.), silver, gold, and platinum; -- so
called from their resistance to oxidation by air and to
dissolution by acids. Copper, mercury, aluminium,
palladium, rhodium, iridium, and osmium are sometimes
included.
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Syn: Honorable; worthy; dignified; elevated; exalted;
superior; sublime; great; eminent; illustrious;
renowned; stately; splendid; magnificent; grand;
magnanimous; generous; liberal; free.
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Radon \Ra"don\ (r[=a]"d[o^]n), n. (Chem.)
An intensely radioactive gaseous element produced by the
radioactive decay of radium-226, which is the main isotope of
radium found in pitchblende. Chemically it is an inert noble
gas. Its atomic symbol is Rn. It has an atomic number of 86.
The radon isotope produced by decay of radium has an atomic
weight of 222.017, and this isotope decays by alpha emission
with a half-life of 3.82 days. Numerous other isotopes have
been observed, all radioactive and all having half-lives
shorter than that of radon-222. Radon was discovered by M.
and Mme. Curie, of Paris, in their studies of the radioactive
substances in pitchblende. Radon was originally called
radium emanation or exradio.
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radon
Symbol: Rn
Atomic number: 86
Atomic weight: (222)
Colorless radioactive gaseous element, belongs to the noble gases. Of
the
twenty known isotopes, the most stable is Rn-222 with a half-life of 3.8
days.
Formed by the radioactive decay of Radium-226. Radon itself decays
into
polonium. Used in radiotherapy. As a noble gas, it is effectively
inert,
though radon fluoride has been synthesized. First isolated in 1908 by
Ramsey
and Gray.
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