Transcription
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-Bohr 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, Bohr 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 atom, 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 nucleides 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 isobars. 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 to 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 isomer. Now, in chemistry, an 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, an 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 technetium 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.