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Longman Dictionary of Contemporary English
▪ Would firms move into areas with high radon concentrations?
▪ Equally high domestic lifetime radon exposures are rarely found.
▪ One area of recent debate concerns radon gas and its links to lung cancer.
▪ In recent years, concern has been raised over exposure to ionizing radiation from radon gas.
▪ As for radon, Rudy said looking for radon in drinking water would be extremely expensive and might not help public health.
▪ But who do we blame for radon?
▪ Environmentalists keep quiet because concern over radon in houses would divert attention from the campaign against nuclear power.
▪ If the soil is permeable enough radon can diffuse out before it decays.
▪ The applicability of such data derived from uranium miners to the general population is central to the radon issue.
▪ They are the noble gases: neon, argon, krypton, xenon, and radon.
▪ This is the so-called Action Level beyond which the occupier is advised to reduce the radon level.
The Collaborative International Dictionary

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.

    Statues, with winding ivy crowned, belong To nobler poets for a nobler song.

  2. Grand; stately; magnificent; splendid; as, a noble edifice.

  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.

    Note: Noble is used in the formation of self-explaining compounds; as, noble-born, noble-hearted, noble-minded.

    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.

    Syn: Honorable; worthy; dignified; elevated; exalted; superior; sublime; great; eminent; illustrious; renowned; stately; splendid; magnificent; grand; magnanimous; generous; liberal; free.

Douglas Harper's Etymology Dictionary

heaviest gaseous element, 1918, from German Radon, from radium (q.v.) + -on suffix of inert gases. The element was identified in radioactive decay of radium. Alternative name niton (from Latin nitens "shining") gained currency in France and Germany.


n. A radioactive chemical element (''symbol'' Rn, ''formerly'' Ro) with atomic number 86, one of the noble gases.


n. a radioactive gaseous element formed by the disintegration of radium; the heaviest of the inert gasses; occurs naturally (especially in areas over granite) and is considered a hazard to health [syn: Rn, atomic number 86]

Radon (disambiguation)

Radon is a chemical element.

Radon may also refer to:

  • Radon, Orne, a town in France
  • Johann Radon, Austrian mathematician
    • Radon transform, a type of mathematical transform
    • Radon measure, a type of mathematical measure
    • Radon space, a metric space in mathematics
  • Rodan, known as Radon in Japanese, a fictional monster in the manner of Godzilla
  • MSBS Radon, Polish assault rifle
  • Jaroslav Radoň (born 1986), Czech canoeist
  • Radon Labs, video game developer in Germany
  • Nova Radon, an Austrian paraglider design

Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as a decay product of radium. Its most stable isotope, Rn, has a half-life of 3.8 days. Radon is one of the densest substances that remains a gas under normal conditions. It is also the only gas under normal conditions that has no stable isotopes, and is considered a health hazard due to its radioactivity. Intense radioactivity has also hindered chemical studies of radon and only a few compounds are known.

Radon is formed as one intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead. Thorium and uranium are the two most common radioactive elements on earth; they have been around since the earth was formed. Their naturally occurring isotopes have very long half-lives, on the order of billions of years. Thorium and uranium, their decay product radium, and its decay product radon, will therefore continue to occur for tens of millions of years at almost the same concentrations as they do now. As radon itself decays, it produces other radioactive elements called radon progeny (also known as radon daughters) or decay products. Unlike the gaseous radon itself, radon daughters are solids and stick to surfaces, such as dust particles in the air. If such contaminated dust is inhaled, these particles can stick to the airways of the lung and increase the risk of developing lung cancer.

Unlike all the other intermediate elements in the aforementioned decay chains, radon is gaseous and easily inhaled. Thus, naturally-occurring radon is responsible for the majority of the public exposure to ionizing radiation. It is often the single largest contributor to an individual's background radiation dose, and is the most variable from location to location. Despite its short lifetime, some radon gas from natural sources can accumulate to far higher than normal concentrations in buildings, especially in low areas such as basements and crawl spaces due to its density. It can also occur in water where the water comes from a ground source -e.g. in some spring waters and hot springs.

Epidemiological studies have shown a clear link between breathing high concentrations of radon and incidence of lung cancer. Thus, radon is considered a significant contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency, radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States. About 2,900 of these deaths occur among people who have never smoked. While radon is the second most frequent cause of lung cancer, it is the number one cause among non-smokers, according to EPA estimates.

Usage examples of "radon".

Sleek Radon - Ulzer fighter engines with scoop-air stabilizers towed the Pod at the end of Steel ton cables.

Qui-Gon caught sight of Anakin appearing through the crowds, riding an eopie with Padme up behind him, towing one of the massive Radon - Ulzer engines.

The Radon - Ulzers hummed anxiously, the energy binders keeping them in sync, the Steelton cables drawing on the racing Pod with just the right amount of give through the wicked turns.

The Radon - Ulzers continued to act in concert, locked together by the energy binders, but the racer was out of control.

Others would throw bursts of hot plasma through a ram field, or carbon vapor to produce sudden surges in the burn rate, or half a ton of pressurized radon gas in a stasis field.

A minute later the radon was in the constriction, and incredible things were happening: radon fusing to transuranian elements, then fissioning immediately.

The stasis box was a soft iron cylinder seven feet long, welded to the shells of two radon bombs to give a total length of fourteen feet.

One day they threw the ram field constriction wide open, andin free fall, protected from the oncoming gamma rays by the scintillating dome of the inner ram fieldthey moved the radon bombs back to their nests in the weapons pod.

Sometimes, alone, he cursed Brennan for using up all of the radon bombs.

But, I thought, radon needed an enclosed space to congregate and the hurricane had ensured there were no enclosed spaces left.

Naturally occurring uranium in the rocks decays into radon gas, which seeps through tiny cracks in the rocks and soil and into the basement, where it gets trapped.

I noticed that Tell Radon was here twelve years longer than standard retirement date.

When suddenly, after holding on for twelve years, Tell Radon decides that he has to retire right now!

It cannot be so, but you would make a better king than Radon, his father had whispered to him as he lay dying.

Best to cross and get as far from the Temple entrance as possible before his half-brother Radon, the future king, sent guards in here after him.