From Page 4
The Infinitesimally Small
The tiniest speck that can be seen under an ordinary microscope is composed of more than ten billion atoms! Yet, in 1897 it was discovered that the atom has tiny orbiting particles called electrons. In time, the nucleus of the atom, around which the electrons orbit, was found to consist of larger particles-neutrons protons. The 88 different kinds of atoms, or elements, that occur naturally on earth are basic all the same size, but they vary in weight because each has a progressively larger number of these three basic particles.
The electrons-in the case of the hydrogen atom, one single electron-whirl through space around the atom's nucleus billions of times every millionth of a second, thus providing shape to the atom and causing it to behave as if it were solid. It would take nearly 1,840 electrons to equal the mass of a proton or a neutron. Both the proton and the neutron are about 100,000 times smaller than the entire atom itself!
To get some idea of how empty an atom is, try to visualize the nucleus of a hydrogen atom in relation to the atom's orbiting electron. If that nucleus, consisting of a single proton, were the size of a tennis ball, its orbiting electron would be about two miles away.
A report on the centennial celebrations of the discovery of the electron commented: "Few think twice about celebrating something no one has seen, which has no discernible size and yet has a measurable weight, an electric charge-and spins like a top...Today no one questions the idea that things we can never see do exist."