The electrons present in the outermost shell or orbit of an atom is called as valence electrons. These electrons are farthest away from the nucleus. The outermost orbit of an atom contains maximum of 8 electrons. These electrons determine the electrical and physical properties of a material. The electrons revolving in the outer most orbit of an atom has highest energy level. Valence electrons are loosely attached to the nucleus. Therefore, less amount of energy is required to pull an electron from the outer most orbits.