The science of nuclear energy
The science of nuclear energy

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The science of nuclear energy

1.2.1 Radioactivity

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JIM AL-KHALILI
In 1896, French scientist Henri Becquerel was working with uranium crystals and found ultraviolet light made them glow. It looks eerie. He left uranium salts overnight on a photographic plate that had never been exposed to light. In the morning, he found a dark shadow on it, and realised that the uranium salts must have been the source of energy. Becquerel had discovered radioactivity.
Scientists began to investigate. One was young Polish chemist Marie Curie.
Marie began collecting uranium ore, called pitchblende. Testing it with an electrometer, she found that it was four times more radioactive than pure uranium. She checked it 20 times. What could be going on?
Then she had a brainwave. She decided there was something else in the pitchblende that was boosting its radioactivity, something more radioactive than uranium. But what? Could it be a new element?
Marie Curie didn’t have a well equipped lab. It was far more basic - a bit like this. One chemist called it a cross between a horse stable and a potato cellar. She had a tonne of pitchblende - some say 10 tonnes-- delivered by horse and cart. And then with just basic equipment like this, she attempted to isolate her mystery elements.
Her experiments had a myriad of complex stages, including potentially lethal processes using highly flammable hydrogen gas.
But all her hard work was worth it. With just her primitive kit, Marie Curie discovered two radioactive elements - polonium, named after her native Poland, and another that would launch an entire industry - radium.
Radium was once the key component in luminous paint. It’s intensely radioactive. The world fell in love with radium, assuming its invisible energy must be good for you.
The French slapped on radium face powder. The Germans ate radium chocolate. The Americans wore radium-branded condoms. But the magic faded when doctors realised that far from boosting health, it triggered cancers.
Marie Curie didn’t live to see the amazing journey the radioactive elements would take us on. Because whilst these are naturally occurring elements, they would take man one step closer to a seemingly impossible dream - to create entirely new elements.
End transcript
 
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Radioactivity was discovered in 1896 by Henri Becquerel who noticed that the radiation from uranium salts had similar characteristics to X-rays that had been discovered the previous year by Wilhelm Röntgen. The uranium salts emitted particles that reacted with photographic plates.

Over the following 20 years, Marie and Pierre Curie, Ernest Rutherford, and many others worked on identifying the different emissions called initially ‘uranic rays’. Marie Curie was working with a uranium ore called pitchblende, and managed to isolate two new elements within the pitchblende – polonium and radium. This was no mean feat as within a tonne of pitchblende there was less than a gramme of these new, highly radioactive elements.

It was discovered that radioactive materials emit particles of three distinct types and that these had differing masses and charges. These three types of emission were called alpha, beta and gamma particles.

You’ll look at these particles in the next section.

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