Basic Atomic Theory, The Structure of Matter
The field of study we call electricity is the investigation of the forces
created by charged particles, especially electrons, and the motion
and interactions of those particles. The electron is a fundamental
component of matter and is considered to have the smallest possible
unit of negative charge. In comparison to ordinary visible objects in
our environment, the electron is an extremely small particle, having a
mass of only 9.109 × 10-31 kg.
Atomic Structure
All matter is composed of atoms, each of which has a central
nucleus and one or more electrons that travel in orbits around the
nucleus, like satellites around the earth. The nucleus contains one or
more positively charged particles called protons. The positive
charge of a proton is ‘opposite’ to the negative charge of an electron,
in the sense that the total, or net, charge of the combination is zero.
Thus, an atom that has the same number of electrons in orbit as it has
protons in its nucleus is electrically neutral. The nucleus of every
atom except that of hydrogen also contains one or more neutrons,
which carry no electrical charge. The number of protons and neutrons
in the nucleus of an atom uniquely determines the element it
represents - iron, copper, oxygen, and so on - and all the atoms of a
given element have identical nuclei.
figure 741.1
