Page 10 - Curriculum Visions Dynamic Book

Radon (Rn)
Element 86. It is an inert, radioactive gas in group 8, the noble gases, in the Periodic Table. It is the heaviest known gas.
Radon is a colourless, odourless, tasteless gas at room temperature
and pressure. However, when cooled below its freezing point (–71°C), solid radon becomes phosphorescent, glowing yellow just below its freezing point, but changing to orange–red at very low temperatures.
Discovery
First observed in 1899 by the British scientists R. B. Owens and Ernest Rutherford.
Technology
Rising levels of radon coming from the ground can be a sign of an increased likelihood of an earthquake. Radon is also used in radiation therapy.
Geology
Radon is produced by the radioactive decay of radium.The atmosphere contains small amounts of radon, especially above rocks like granite
as a result of seepage from the radioactive decay of uranium in these rocks.
Biology
It is not found in living things. High levels of radon gas may be a health hazard, especially for people who live on areas of granite rock where high levels of radon are produced by the decay of uranium. Radon also occurs in some spring waters.
Key facts...
Name: radon
Symbol: Rn
Atomic number: 86
Atomic weight: 222
Position in Periodic Table: group 8 (18)
(noble gases); period 6
State at room temperature: gas
Colour: colourless
Density of gas at 20°C: 9.2 g/l
Melting point: –71°C
Boiling point: –62°C
Origin of name: radon was originally called niton,
from the Latin word nitens, meaning shining. In 1923 the name was changed to radon after the element radium.
Shell pattern of electrons: 2–8–18–32–18–8
10