Radon

Category: noble gas Atomic number: 86 Colour: glowing orangey red in solid form, otherwise colourless Melting point: −71°C (−96°F) Boiling point: −62°C (−79°F) First identified: 1900

You may be alarmed to hear that there is a colourless, odourless, radioactive gas that is constantly seeping from the ground, and that can build up in dangerous quantities in poorly ventilated basements (especially in granite buildings). Radon is the first of two radioactive noble gases that complete the bottom right-hand corner of the periodic table. It is formed through the decay of small quantities of uranium in the soil, in a pathway also including radium, thorium and actinium. In turn, it has a short half-life and rapidly decays into polonium, then bismuth, then lead.

Radon can be collected by placing a glass jar over a piece of radium. It was first described by the German chemist Friedrich Ernst Dorn as a ‘radium emanation’ – a gas that appeared to make the air around a piece of radium radioactive. Ernest Rutherford and William Ramsay subsequently had a slightly bitchy dispute over who was the element’s true discoverer.

Its short half-life means that when radon does gather in a building, it will gradually disappear, but there have been cases in which it can be quite damaging – it can, for instance, contribute to causing lung cancers. There are home testing kits available if you are worried about your own basement. However, most radon passes fairly harmlessly into the atmosphere, of which it forms a minute proportion while it decays.