Basic Electrical Theory ATOM AND ITS FORCESThere are two simple rules concerning electron shells that make it possible to predict the electrondistribution of any element:1. The maximum number of electrons that can fit in the outermost shell of any atomis eight.2. The maximum number of electrons that can fit in the next-to-outermost shell ofany atom is 18.An important point to remember is that when the outer shell of an atom contains eight electrons,the atom becomes very stable, or very resistant to changes in its structure. This also means thatatoms with one or two electrons in their outer shell can lose electrons much more easily thanatoms with full outer shells. The electrons in the outermost shell are called valence electrons.When external energy, such as heat, light, or electrical energy, is applied to certain materials, theelectrons gain energy, become excited, and may move to a higher energy level. If enough energyis applied to the atom, some of the valence electrons will leave the atom. These electrons arecalled free electrons. It is the movement of free electrons that provides electric current in ametal conductor. An atom that has lost or gained one or more electrons is said to be ionized orto have an ion change. If the atom loses one or more electrons, it becomes positively chargedand is referred to as a positive ion. If an atom gains one or more electrons, it becomesnegatively charged and is referred to as a negative ion.Rev. 0 Page 7 ES-01
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
