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The ancient Greeks had a word for it. Records show that as early as
600 BC the attractive properties of amber were known. Thales of
Miletus (640-546 BC), one of the "seven wise men" of ancient
Greece, is credited with having observed the attraction of amber for
small fibrous materials and bits of straw. Amber was used by these
people, even as it is now, for ornamental purposes. Just as the
precious metals had their names of gold and silver, so amber had its
name: "electron." It was later shown that the same effect can be
obtained by rubbing a rod of glass or hard rubber with a
handkerchief. Many other nonmetallic materials are found to have this
property, which is known as "static electricity."
All electrified materials behave either as glass or rubber. Glass has
a "positive" charge and hard rubber has a "negative" charge. If you
electrify two strips of hard rubber by rubbing them with fur, they
will repel each other. Two glass rods will behave the same way. But,
if you electrify a rod of rubber and suspend it near an electrified
rod of glass, they will attract each other. One of the most important
laws of electricity is "Bodies with similar charges repel each other;
bodies with opposite charges attract each other." A positive charge
is designated with a (+); a negative charge by the sign (-).
Although people have controlled electricity for many years, no one
can explain exactly what it is. Many different theories have been
given as to the nature of electricity through the years, but the
modern one is the "Electron theory." In short, the electron theory
proposes that all matter consists of tiny particles called molecules.
These molecules are made up of two or more smaller particles called
atoms. The atoms are then divided into smaller particles called
protons, neutrons, and electrons. These particles are all the same in
matter, whether in gas, liquid, or solid. The different properties or
characteristics of the matter take form according to the arrangement
and numbers of these particles which make up the atom. The proton has
a natural positive charge of electricity; the electron has a negative
charge; and the neutron has no charge at all, but just adds weight to
the matter.
Protons and neutrons form the central core of the atoms about which
the electrons rotate. The electrons carry small negative charges of
electricity, which neutralize the positive charges of the protons.
The simplest atom of all is the hydrogen atom. It consists of one
positive proton and one negative electron. Other atoms, such as those
forming copper, iron, or silicon, are much more complicated. Copper,
for example, has 29 electrons circling about its nucleus in four
different orbits. While protons are much smaller than electrons in
size, they contain the bulk of the mass of every atom. One proton,
for example, weighs nearly two thousand times as much as an electron.
The electrons therefore are light particles or objects around a small
but relatively heavy nucleus.
It is difficult to conceive the size of the atom. Research by
physicists has established that the mass on one electron is about
.000,000,000,000,000,000,000,000,000,911 of a gram. If you assume
that one proton in a hydrogen atom is the size of a baseball in
Kansas City, then the electron would have an orbit which would reach
from the Atlantic coast to the Pacific. Along with the extremely
small size of electrons and protons, they are separated by relatively
vast distances.
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