Embedded Systems Circuits and Programming

Appendix B

Essential Electronics

B.1 Atom

Until the end of the nineteenth century it was assumed that matter was composed of small, indivisible particles called atoms. The work of J.J. Thompson, Rutherford, and Bohr proved that atoms were complex structures that contained both positive and negative particles. The positive ones were called protons and the negative ones electrons.

Several models of the atom were proposed: the one by Thompson assumed that there were equal numbers of protons and electrons inside the atom and that these elements were scattered at random, as in the leftmost drawing in Figure B-1. Later, in 1913, Rutherford’s experiments led him to believe that atoms contained a heavy central positive nucleus with the electrons scattered ...