Page 22 - Curriculum Visions Dynamic Book

Radium
Radium (chemical symbol Ra) is a radioactive element with chemical properties similar to those of calcium and barium.
Its name comes from the Latin radius, meaning “ray”. Radium was the first radioactive element ever discovered, and the word radiation also comes from the same Latin source.
Radium is found combined with the more widely
known radioactive element uranium. In 1896 Antoine
Henri Becquerel discovered by accident that a compound of uranium caused photographic plates to become fogged just as though they had been exposed to light. From this observation
it became clear that the ore was sending out invisible rays that had the same effect on the photographic plate as light rays. The difference was that these rays could penetrate materials such as paper and wood and thus fog a photographic plate even though it had been carefully wrapped up.
Marie and Pierre Curie refined many tonnes of uranium
ore (pitchblende) before they found the element radium.
(It is usual to find just one gram of radium in every seven tonnes of pitchblende!)
Radium is found alongside uranium because it is one of the elements formed by the transmutation of uranium as it decays (see page 10). However, far more uranium will already have become lead, so that only one part in three million of uranium has still to become radium (and this, in time, will also become lead).
Because radium was one of the first radioactive elements
to be examined, the way it changes with time has been used
as the measure of radiation. The units of radiation, the becquerel and the curie, are named after these early pioneers.
Most compounds of radium are colourless when first prepared, but they become coloured upon standing, because the intense radiation causes changes in the atoms of the compounds.
Radium is little used today.
 Marie and Pierre Curie at work in their laboratory in France, 1903.
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