Strong Nuclear Force - This force is even stronger than the electromagnetic force and is responsible for holding nuclei together. The fact that this force is much stronger than the electromagnetic force is the primary reason that nuclear reactions involve much more energy than chemical reactions. In recent years, it has been discovered that this force is closely related to the electromagnetic force. The nuclei of atoms may be broken apart or combined to form new elements, sometimes releasing great amounts of energy. Nuclear reactions occur when nuclei collide at high speeds such as during a nuclear explosion, in a more controlled fashion in a nuclear power plant, and at the center of stars.
Many nuclei are unstable and decay spontaneously.
Although these nuclei are unstable they decay in a predictable manner. This is useful for dating geologic samples and archeological artifacts as demonstrated in your homework.