L9.1 Nuclear Physics: Introduction

Key Takeaways

welcome back to 8701 we're starting a new chapter now chapter 9 on nuclear physics and this video is the first introduction into the topic where i'm explaining some of the terminology and some of the concepts we'll dive in much more detail as we go on so given an atom you can specify the number of neutrons the number of protons and the number of electrons which is equal to the number of protons for neutral atoms atoms of the same element they have the same atomic number z but they're not all the same isotopes of the same element have different number of neutrons so you can have uranium with a num number of neutrons varying um you typically you know write an isotope by specifying the mass the number of protons and the number of neutrons but that information is redundant so typically we we simplify this by just writing things like 238 uranium and that specifies that specifies a specific isotome of uranium when talking about different nuclei we sometimes refer to them as nucleate atom nucleus with a specific number of neutrons and a specific number of protons isobars are nuclei nucleate with the same mass with the same number of names some of the same sum of protons and neutrons but with varying individual number of protons on the drugs an isotone is a nuclear with the same number of neutrons but with varying number of protons and an isomer is the same nuclei but the different eigenstates which means that the energy states sorry different energy state so we can excite nuclei with their compound particles the nuclear radius is typically um can be extracted from the mass of the of the nuclei and it's simply then we add little balls to the sum and it scales with um a to the one-thirds the mass of the number of elements in this in this in this nuclide there's many isotopes there's many nuclei and so you typically have uh you can can look at all of them if you want or subset of them in nuclear shards as given here where we've got z the number of protons and here the number of neutrons [Music] and we'll we'll look at many more of those charts later here's another representation of the very same thing you see in nuclear shard again um and here what's plotted in red are the stable nuclei we will see that nuclei can decay and will understand why they decay and in what form they decay that is the core part of this of this chapter it's understanding how nuclei can decay and what we can learn about them uh by studying the case um one way to look at it for example you see that here i plot z over a so the number of protons over the over the sum of the number of protons z plus n and you see that most of the stable nuclei with the exception of the one with very small mass number have less protons than neutrons so there is an axis of neutrons it can also be seen here the stable nuclei are typically on or below this axis where z is equal to n radioactive decays can be characterized typically there is a parent nuclide and there's a daughter nuclei and so radioactive decay is a process in which an unstable nuclei spontaneous rules energy by emitting high particles ionization particles and radiation the decay and the loss of energy results then in an atom of one type the parent particle of paranuclei transforming into an another type of an item called the daughter nuclei we have already looked at [Music] decay rate in the concept of particle physics interactions but we can define this very similar here the decay rate or sometimes this is called decay constant and then as we did before we can define the mean lifetime or the half lime life of apparent nuclei so this is it for the introduction and we in the next lecture we'll start looking in in the energy which is used to bind the nuclei the the protons and neutrons together and how we can understand this from an empirical model you