PHYS 221 Recitation Kevin Ralphs Week 14

Overview Nuclear Physics – Structure of the Nucleus – Nuclear Reactions

Nuclear Physics

Structure of the Nucleus – Forces within the Nucleus Electric Forces due to repulsion between protons The strong nuclear force is an attractive force that binds nucleons together, but only acts over short distances – Stability of the Nucleus The above forces work together to create an equilibrium within the nucleus Although neutrons add stability by spacing the protons further apart to counterbalance their electric repulsion, adding too many create an unstable nucleus that will split

Nuclear Physics Nuclear Reactions – Radioactive decay is a spontaneous process where a nuclei splits into two or more particles – The original nucleus is referred to as the parent nucleus with the final result being called decay products

Nuclear Physics Nuclear Reactions – There are 3 kinds of decay that we will concern ourselves with: Alpha Particles – An alpha particle is a cluster of 2 protons and 2 neutrons, essentially a helium nuclei – In this type of decay, the alpha particle is ejected with the appropriate numbers adjusted in the daughter nucleus Beta Particles – Beta decay occurs when a proton turns into a neutron or the other way around – When this happens, additional particles are kicked out to conserve charge and some other properties that are beyond the scope of our class Gamma Decay – Nucleons can become excited and emit photons, gamma rays, when they return to their ground state just like electrons

Nuclear Physics Nuclear Reactions – Conservation Rules Conservation of Mass-Energy Conservation of Momentum Conservation of Electric Charge Conservation of Nucleon Number

Nuclear Physics Nuclear Reactions – Binding Energy If we were to total up the individual masses of the nucleons and compare this to the atomic mass of them together, we would notice that some of the mass is missing We should expect this: The nucleus is stable so it should be a lower energy system than the individual nucleons Due to relativity, we know that this lower energy has to be accounted for with lower mass Note that when doing binding energy calculation, you have to carry many digits since the change is mass is very small

Nuclear Physics