TABLE OF CONTENTS We saw in Chapter 14 that studies of the atom indicated that the atom consists of a very small, positively charged nucleus surrounded by negatively charged electrons. Experiments on the scattering of ? particles revealed that the nucleus has dimensions of the order of 10 -14 m. Since the diameter of an atom is of the order of 10 -10 m, the nucleus takes up only a minute fraction of the volume of an atom. The nucleus, however, contains nearly all of the mass of the atom, as was also shown by the scattering experiments.
The existence of the atomic nucleus (named by analogy with the nucleus of a living cell) and its properties raised many questions similar to those raised about the atom. Is the nucleus itself made up of still smaller units? If so, what are these units, and how are they arranged in the nucleus? What methods can be used to get answers to these questions? What experimental evidence can be used as a guide?
The study of the properties and structure of atoms needed new physical methods. The methods that could be used to study the properties of bodies of ordinary size, that is, those with dimensions of the order of centimeters or meters, could not yield information about the structure of atoms. It is reasonable to expect that it is still more difficult to get information about what goes on inside the nucleus, which is such a...
