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Radon

Radon, the heaviest noble gas, was discovered from the decay of radium. It is odourless and colourless at room temperature. It phosphoresces to a yellow color below its freezing point (-71°C). The color changes to orange-red when air liquefies.

Because radon is located in the soil and rocks, the gas is used as an earthquake detector. Forthcoming earthquakes cause the levels of radon to fluctuate and generally increase in surrounding areas. Radon also serves as a source of radiation for cancer therapy and a radioactive tracer for gas leaks.

Although this noble gas is relatively inert chemically, it is still considered a health hazard because it gives off alpha particle radiation. It is known that radon from surrounding soil and rocks can leak into the basement of homes. Prolonged exposure to large amounts of radon can lead to lung cancer and a decrease in the number of red blood cells, causing anaemia.