GC: n
CT: Radon is the main source of exposure to natural radioactivity for humans because it is the only descendant of uranium to exist in a gaseous state. This allows it to leave the surface of a rock containing some uranium and enter the atmosphere. Its ability to escape from underground volcanic and granite-based rocks and enter the air that surrounds us has made radon exposure a ubiquitous feature of our terrestrial environment. A few tens of grams of radon on the Earth surface are all that is needed to make it the most significant contributor to natural radioactivity levels. This astonishingly small quantity is the consequence of radon-222 half life, which is very short by comparison to that of radium and even more when compared to that of uranium 238. According to the law of radioactive equilibrium, radioisotopes in a radioactive sery have an abundance inversely proportional to their half-lives: one atom for 154,000 radium atoms and one for 430 billion uranium 238 atoms.
S: RAD – https://goo.gl/kTBdgw (last access: 16 November 2017)
N: 1. heaviest gaseous element, 1918, from German Radon, from radium (radioactive metallic element, 1899, from French radium, named 1898 after identification by Marie Curie and her husband, formed in Modern Latin from Latin radius “ray”) + -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.
Its symbol is Rn.
2. A radioactive inert gas, atomic number 86, the decay product of radium. The most stable isotope, radon-222, has a half-life of 3.825 days.
3. Relatively high concentrations of radon may occur in mines and inside buildings built above certain rocks, such as granite. This is regarded as a health hazard requiring remedial measures, although currently unconfirmed research suggests that the danger in homes may have been overestimated.
4. This element belongs to the group O (inert gases) of the periodic table formed by the disintegration of radium.
5. The first known use of this term was in 1918.
6. Radon is the second leading cause of lung cancer in the United States, responsible for thousands of deaths each year. Exposure to radon causes no immediate symptoms, but the long-term threat of lung cancer is significant to everyone. People who have never smoked make up approximately 2,900 of the estimated 21,000 radon-related lung cancer deaths each year.
S: 1. OED – https://goo.gl/bxfmLh; http://goo.gl/cDsC61 (last access: 18 November 2017); Collins – https://goo.gl/4aHZBu (last acces: 18 November 2017). 2 & 3. OR – https://goo.gl/HT4pNj (last access: 16 November 2017). 4. TERMIUM PLUS – https://goo.gl/5tDrsY (last access: 16 November 2017). 5. MW – https://goo.gl/ip99vm (last access: 16 November 2017). 6. ALA – https://goo.gl/cz9NLF (last access: 16 November 2017).
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