hello and welcome to the Radiology tutorials Physics course now we're going to start this course off by having a look at the basic atomic structure now as I'm sure you're aware atoms are comprised of atomic particles known as protons neutrons and electrons the positively charged protons and neutral neutrons are packed tightly together in a central core known as the nucleus and the negatively charged electrons orbit around that Central nucleus and this is what's known as the Rutherford bore model of the atom now much like planets orbit around the sun these electrons orbit around the nucleus and they are holding place instead of gravity like the planets are holding place they hold in place by the electromagnetic force the force of attraction between this negative electron and positive protons in the nucleus now boar actually discovered that these electrons exist in what's known as energy shells or electron shells and the energy of those shells are specific for each and every element now the number of protons within the nucleus of an element is what defines that element and in an uncharged atoms the number of electrons will equal the number of protons within the nucleus now we have a standard way of writing specific elements within the periodic table and we use this basic notation for elements this x represents the chemical symbol of that element and as I've said the number of protons in that element defines the element's chemical symbol and this is what's known as the atomic number of that element we denote it by the letter Z here so the number of protons will determine the chemical element so for every atomic number we will have a specific chemical symbol now the mass number is the number of protons and neutrons combined it's an integer it's a whole number we add the total number of protons to the total number of neutrons now as you'll see we can use carbon as an example carbon has six protons the atomic number of carbon is six if this atomic number was to change if this was to go to seven or eight it would no longer be called carbon now the majority of carbon that we find in our atmosphere is known as carbon-12 it's got a mass number of 12 six protons and six neutrons and in an uncharged carbon atom there would be six electrons now if we were to change the total number of neutrons in the nucleus but kept the protons the same it would still be called carbon but it would no longer be carbon-12 if we were to add a neutron it would be called carbon 13 and this is what's known as an isotope now when we are describing atoms or elements within our universe we call those nucleides that's the broad overarching term and we can subdivide nuclides into multiple different categories and you'll see throughout this course we'll be using these names and it's useful to know the classification of nuclei so as I've mentioned carbon has six protons its atomic number is six but we can change the number of neutrons and that is what's known as an isotope now the easy way to remember this is isotope has a p here the protons remain the same still called carbon we also then get ISO bars now you'll know that our mass number was denoted by the letter A so isobars with the letter A have the same mass number but different atomic numbers the number of protons change you can see because the number of protons change the chemical element itself changed molybdenum to technetium but our atomic number isn't the same this is what's known as an isobar isotones the letter N have the same number of neutrons but different atomic numbers so iodine 131 which is a radioactive isotope of iodine is an isotone two Xenon 132 these both have 78 neutrons within their atoms so these are isotones of one another we then get what is known as an ISO myrrh now in chemistry and isomer is something that has the same molecular formula but a different shape you can think of it as your hands they look the same they've got the same makeup but they are mirror images of one another they can't actually fit directly over one another now when we talk about nuclear physics and isomer is similar it has the same atomic components the same number of protons neutrons and electrons but the energy configuration of that atom is slightly different so we get what is known as a metastable version of an atom the atomic constituents of these two technium atoms here is the same but the energy levels different and this is what is known as an isomer we can use this e here to remember that the energies are different and I'm just telling you that these classifications exist as we go especially into our nuclear medicine module we're going to dive deeper into these various different classifications so in our next talk we're going to look deeper into the energy levels and look at electron orbital Tools in particular and then after that we're going to further subdivide these basic Atomic constituents into subatomic particles where we enter the realm of quantum physics so I'll see you all there goodbye