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Structure of Matter

Author: Leonard Krugman

For many years, the atom was considered to be the smallest particle of matter. It is now known that the atom is composed of still smaller entities called electrons, protons, and neutrons. Each atom of any one element contains specific quantities of these electrical entities.


Fig. 1-1. The carbon atom.

Physically, the electrons rotate around the core or nucleus of the atom, which contains the protons and neutrons. Figure 1-1 illustrates the layout of a carbon atom. A carbon atom contains six each of electrons, protons, and neutrons. Note that the six orbital electrons do not rotate at equal distances from the nucleus, but rather are restricted to two separate rings. With respect to the size of these electrons, tremendous distances exist between the electrons and the nucleus. If it were possible to magnify the atom by a factor of 1014, that is, one hundred thousand billion times, the electrons would be the size of basketballs, with an orbit spacing of approximately 12 miles.

The negative electrical charge of the electron is exactly equal and opposite to the charge of the proton. The neutron has no charge. The electron is three times larger than the proton, but its mass is only .0005 that of the proton. In an electrically balanced atom, as illustrated in Fig. 1-1, there is an equal number of electrons and protons.

Gravitational, electric, magnetic, and nuclear forces all act within the atom. These forces tend to keep the electrons revolving in their orbits around the nucleus at tremendous speeds. As might be expected, the electrons located in rings close to the nucleus are tightly bound to their orbit and are extremely difficult to dislodge. The outer or so-called valence-ring electrons are, comparatively speaking, loosely bound to their orbit. The ease or difficulty with which electrons can be dislodged from the outer orbit determines whether a particular element is a conductor, insulator, or semiconductor.

Last Update: 2010-11-17