A Brief History of Radioactivity
More than one hundred years ago, Henri Becquerel discovered that uranium emitted penetrating rays similar to those used by Wilhelm Röntgen to take the first X-ray image (of his wife’s hand), starting a new era of far-reaching applications. There are of course many dangers that come with the use of radioactivity, but there are also many beneficial uses for our society. WHAT IS RADIOACTIVITY An alpha particle is expelled from the nucleus. The nucleus of an atom is made of protons and neutrons. Because protons have positive charge, they repel each other, so there must be a force that holds the nucleus together, and the neutrons don’t help, because they are neutral. This force is the strong nuclear force and the energy associated with it is called the binding energy. For reasons that go beyond the scope of this article, atomic nuclei with more than 83 protons in it (bismuth) do not have enough binding energy to hold the nucleus together. In response, the nucleus tries to achieve bala...