Electron (Encyclopedia of Science)
The electron is a subatomic (smaller than an atom) particle that carries a single unit of negative electricity. All matter consists of atoms that, in turn, contain three very small particles: protons, neutrons, and electrons. Of these three, only electrons are thought to be fundamental particles, that is, incapable of being broken down into simpler particles.
The presence or absence of an excess of electrons is responsible for all electrical phenomena. Suppose a metal wire is connected to two ends of a battery. Electrical pressure from electrons within the battery force electrons in atoms of the metal to flow. That flow of electrons is an electric current.
Electron energy levels
The protons and neutrons in an atom are packed together in a central core known as the nucleus of the atom. The size of the nucleus is many thousands of times smaller than the size of the atom itself. Electrons are distributed in specific regions outside the nucleus. At one time, scientists thought that electrons traveled in very specific pathways around the nucleus, similar to the orbits traveled by planets in the solar system.
(The entire section is 1289 words.)
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