Suppose we have a single particle moving in one dimension whose potential energy as a function of x x is u ( x ) u(x). show (using the chain rule and the relationship f ( x ) = − u ′ ( x ) f(x)=−u′(x)) equation (4) (4), conservation of energy, for this system.

Students should realize that each atom in a group has the same number of electrons in its outermost energy level. For instance, hydrogen, lithium, sodium, and potassium all have 1 electron on their outer energy level. Let students know that these electrons in the outermost energy level are called valence electrons.