Nuclesar

The energy of a nuclear bomb comes from inside the nucleus of the atom. Mass is converted into energy according to E = mc2. This energy is the binding energy of the nucleus, the glue that keeps the nucleus of the atom together.

Radiating particles

In some cases, the nuclear force is not able to keep a nucleus all together, and the nucleus loses some of its particles. French physicist Henri Becquerel accidentally discovered this effect in 1896. He'd been intrigued by the experiments with x-rays that Wilhelm Roentgen had been doing in Germany. Becquerel obtained a uranium salt to see if he could observe these x-rays.

In his laboratory at the Museum of Natural History in Paris (where his father and grandfather had also been physics professors), Becquerel started his experiments by exposing to the sun a photographic plate with the uranium salt sprinkled on it, thinking that sunlight would activate the x-rays. One cloudy day when he couldn't perform one of his experiments, he placed the photographic plate with the uranium salt in a drawer. A few days later, he went ahead and developed the plate anyway, thinking that he was going to get a faint image. But the image was very sharp, with high contrast. He soon realized that he'd discovered a new type of energetic radiation.

When Pierre and Marie Curie heard of Becquerel's experiment, they began to search for other elements that could emit similar rays. They found that thorium and uranium emit the same radiation. And in 1898, they discovered two new elements: polonium (named after Marie's native Poland) and radium. The Curies named the effect radioactivity.

In England, Ernest Rutherford designed experiments to investigate this new radioactivity phenomenon and was able to show that these rays come in two varieties, one more penetrating than the other. The less penetrating one, which he called alpha,

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