Thomson’s and Nagaoka’s Atomic Models

The conception of the atom underwent a profound transformation with the discovery of the electron in 1897 by J.J. Thomson. In fact, the existence of an atomic constituent made even more urgent and important the need to provide an answer to the questions “How are atoms composed?” and “What structure do they have?”. Among the various atomic models of the early twentieth century, two of a certain importance were proposed in 1904: that of J.J. Thomson and that of H. Nagaoka. In this chapter, we will introduce both of them by discussing their respective very different structures, characteristics, strengths and limitations together with their role in the development of physics. Along the pages, while dealing with the problem of the constitution of matter, we will discuss also the models proposed by J.B. Perrin, P. Lenard and J.H. Jeans.