1. Aim: How are protons held together within the nucleus? Essential Questions : Why do certain elements undergo radioactive decay and others don’t? How do the nuclei of atoms stay intact if protons are positive, and like charges repel? Describe the various types of radioactive decay in terms of charge, mass and “penetrating power.”

2. Aim: How are protons held together within the nucleus? Do Now: Copy vocabulary and answer questions: Nucleons- protons and neutrons in the nucleus Nuclide- any combination of these protons and neutrons 1. What are the subatomic particles found in the nucleus? 2. How do the nuclei of atoms stay intact if protons are positive, and like charges repel?

3. Aim: How are protons held together within the nucleus? Electrostatic repulsion- occurs between protons in the nucleus Binding forces (strong nuclear force)-overcomes electrostatic repulsion when nucleons are VERY close together The nucleus is at a lower energy state than are its separated nucleons due to strong nuclear foa. Binding energy comes from loss of mass; “mass defect.” Separated nucleons nucleus + energy

4. Aim: How are protons held together within the nucleus? Predicting nuclear stability: 1. Except for smallest nuclei (H and He), all stable nuclei contain a number of neutrons that is equal to or greater than the number of protons. 2. A nucleus with too many or too few neutrons is unstable. 3.Nuclei with even numbers of nucleons are more stable. Band of StabilityBand of Stability Graphing Band of StabilityGraphing Band of Stability