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THEORY OF ATOM
87 matter. Half a century ago, it was believed that the atom is indivisable. By and by, as the radio-activity of certain elements, which transform themselves by natural distintegration came to light, it was presumed that it is possible to disintegrate the atom. In course of time it became known that the nuclei of various elements are loaded with tremendous amount of internal energy that can be liberated by the processes of nuclear fission of heavier elements and nuclear fusion in case of lighter ones Trenendous efforts of scientists in this direction created the Atom bomb Uranium is the only natural element used so far for making a fissiontype Atom bomb There is another element called Plutonium (Pu-239), but this is not a natural element. It is an artificial man-made element with atomic number 94 37 Uranium being naturally radio-active, nuclear fission of its atoms has been comparatively easy Uranium has several isotopes, but the two best known of them are U-238 and the famous U-235. The latter is the only easily fissionable substance It does not exist in nature in a pure form, but is always diluted by the heavier unfissionable U-238 (7% of U-235 and 99 3% of U-238) Pure U-235 must be separated from U-238 to make an Atom bomb.
A Hydrogen-bomb is, on the other hand, a fusion type bomb In this case the nuclei of hydrogen are fus
37 It should be remembered that only a small fraction of the mass is transformed into energy.
