THE STRUCTURE OF ATOMS

Atoms are not solid but composed of three fundamental particles: electrons, protons, and neutrons arranged in various combinations. The electron is defined as being negatively ( - ) charged and revolves around the nucleus of the atom in various concentric paths called orbits. The proton is defined as being positively ( + ) charged. Neutrons are defined as being uncharged or neutral. Protons and neutrons are tightly bound together within the atoms nucleus and are not free to orbit. In an atom the number of negative electrons and positive protons are the same making it electrically neutral. The number of protons present within the atoms nucleus specifies its atomic number. The corresponding numbers of electrons are arranged in different elliptical orbits, called shells, around the nucleus. Electrons in different orbits can rotate around the nucleus in all directions, thus producing a three-dimensional atom. The electrons in the nearest orbit having a great force of attraction while the electrons in the farthest orbit having the least force of attraction. Electrons in the farthest orbit which are loosely held to the nucleus are called valence electrons and therefore rotate around the valence shell. Copper for instance, has one valence electron.

The loosely held electrons in the outer shell often break free due to an input of energy such as heat allowing them to move randomly around through the space in between the various orbits of the other atoms. Such loose electrons are called "free electrons". An atom that loses an electron in this way is left positively charged since it now has an excess of protons. If more electrons attach themselves to the valence shell, then there are more electrons than protons and the atom becomes negatively charged.

THE UNIT OF CHARGE

The unit of charge is the Coulomb, C. The symbol of electric charge is Q. The charge of one electron is given as: 1.6x10^-19, so one Coulomb of charge is equal to 1/ 1.6x10^-19 or 6.25x10¹⁸ electrons.

Q = 1 Coulomb = charge of 6.25 x 10¹⁸ Electrons