1. Changes in the Nucleus Objectives: 1. Describe the changes that accompany nuclear reactions. 2. Define radioactivity. Key Terms: nuclear reaction, strong nuclear force, radioactive decay, nuclear equation

2. Nuclear Stability Although the nucleus is crowded with like charges, the protons do not repel each other. They are held together by a strong nuclear force. This strong nuclear force is increased by the addition of the neutral neutron (no repulsive force). The giving off of nuclear particles (radiation) occurs in radioisotopes as the nucleus attempts to gain stability. No amount of pressure or temperature will speed up or slow down a nuclear reaction. The nuclear radiation is the result of having too many or too few neutrons relative to the amount of protons present.

3. Nuclear Stability Atoms with atomic numbers 1-20 are stable with the equal numbers of neutrons and protons Above atomic number 20, increasing amounts of neutrons are required to stabilize the nucleus At atomic number 83, no amount of neutrons can make the atom stable - all are radioactive Adding extra neutrons to a stable atom can make the atom radioactive C-12, C-13, C-14 (not stable)

4. Types of Radioactive Decay Alpha Consists of 2 protons & 2 Neutrons - Helium Core (no electrons) Low penetrating power - easily stopped by paper or clothing Can travel only a few centimeters through the air Does not pose a health hazard in the amount present in the environment Nuclear equation:

5. Types of Radioactive Decay Consists of a high speed electron The electron is formed in the nucleus when a neutron is converted into a proton and a high speed electron Has essentially no mass About 100 times more penetrating than the alpha particle Can pass through clothing and damage skin Nuclear Equation Negative beta emission Positive beta emission

6. Types of Radioactive Decay Gamma Energetic form of light similar to X-ray Has no mass - does not affect atomic # or mass # Often accompanies alpha and beta radiation Can travel through tissue and solid material - stopped by concrete and lead