Studying the structure of atoms is a little like studying wind. Because you cannot see air, you must use indirect evidence to tell the direction of the wind. You might notice which way fallen leaves move as they are pushed by the wind, and infer that the leaves and wind are moving in the same direction.

Atoms pose a similar problem because they are extremely small. Even with a microscope, scientists cannot see the structure of an atom. In this chapter, you will find out how John Dalton, J. J. Thomson, Ernest Rutherford, Niels Bohr, and other scientists used evidence from experiments to develop models of atoms.