The Nucleus Objectives: Relate nuclear stability to the ratio of neutrons to protons Describe the forms of radioactive decay Balance decay equations

The Nucleus Definitions: nucleons-protons and neutrons collectively nuclide- a specific atom (in nuclear chemistry) mass defect – difference between the actual mass of an atom and the sum of the masses of all of an atom’s protons, neutrons, and electrons Nuclear binding energy – energy released when a nucleus is formed from nucleons (E = mc2)

Binding Energy per Nucleon Higher binding energy/nucleon  higher nuclear stability

Band of Stability Small atoms tend to have neutron-proton ratios ~ 1:1 The ratio approaches 1.5:1 as the atomic number increases Explained by the relationship between strong nuclear forces and electrostatic repulsion

Nucleons and nuclear stability Strong nuclear forces act over very short distances As the # of protons increases, the electrostatic force between protons increases More neutrons are needed to stabilize the nucleus

Nuclear Reactions Transmutation – transformation of one element into another Nuclear reactions occur when unstable nuclei undergo changes in the # of protons and neutrons in order to increase stability Large amounts of energy are given off

Nuclear Reactions In nuclear equations, the sum of atomic #’s and mass #’s must be equal on both sides of the equation.

Complete the following nuclear reactions: