Teaching Radioactivity and Half Life

Background:

The nuclei of certain atoms are stable and under ordinary circumstances, stable nuclei do not undergo change. The nuclei of other atoms are unstable. These nuclei undergo change spontaneously, that is, without outside help. When unstable nuclei undergo change they give off radiation. Atoms which have unstable nuclei are radioactive and are called radioisotopes or radionuclides. The change that an unstable nucleus undergoes is called disintegration or decay. When unstable nuclei disintegrate or decay, certain particles - alpha or beta particles - or bundles of energy called gamma radiation, are emitted. Atoms and molecules in the path of radiation are ionized, that is, they are stripped of electrons. That means alpha particles, beta particles, gamma radiation, and other nuclear emissions have enough energy to remove some electrons from atoms or molecules with which they collide. Positively charged particles and free electrons are left behind after the collisions. Devices that are used to detect radioactivity are based on the ionizing ability of radiation. One such device is the Geiger-Muller tube which is connected to a counter and is commonly referred to as a nuclear scaler. When a charged particle or gamma radiation enters the Geiger-Muller tube, it ionizes many of the argon gas atoms in the tube. The electrons are attracted to the anode and the argon ions are attracted to the cathode. This produces a surge of current which can be counted by the scaler.