Alright. So here in this video, we're going to talk about some atomic properties. Each atom of an element has unique properties, and we're going to talk about 3 specific properties that you all should be familiar with. Now, the very first property that you all should be familiar with is the atomic number.
The atomic number is defined pretty simply. It's a straightforward idea. All it is is the total number of protons in the nucleus of an atom. To get the atomic number, count up the total number of protons, and that's it. The atomic number, or the total number of protons, is actually what defines each element.
If we change the total number of protons in the nucleus of an atom, then we change the element that it falls under. However, if we change the other subatomic particles like neutrons or electrons, then we do not change the element. Only changing the number of protons or only changing the atomic number will change the element, and that's why the atomic number, or the number of protons, defines each element. Let's take a look at our example down below to clear some of this up. We're taking a look at the atomic properties of a carbon atom, more specifically, the carbon atom that we're showing you right over here.
If we want to determine the atomic number, which is once again just the number of protons in the nucleus, all we need to do is count up the total number of protons in this nucleus over here. When we do that, what we'll see is that there are a total of 6 protons in the nucleus, which means that the atomic number of this atom is 6. The protons are here in red, and we're just counting up the number of red circles here, and there are 6 of them, which is why the atomic number is 6. So that's pretty straightforward.
If we were to add a 7th proton in here, then we would be changing the element, and it would no longer be carbon. Instead, it would be nitrogen. The number of protons in the nucleus defines the element. If we were to add another neutron here, pretend this were a gray circle, if we were to add another neutron then it would still be a carbon atom. If we were to add another electron, revolving around the nucleus, then it would also still be a carbon atom, and so, the number of electrons and neutrons do not affect the type of element that it is.
Moving on, what we have next is the mass number, and the mass number is also a pretty straightforward idea. It's really just the mass of the nucleus of a single atom.
If we want to take the mass of the nucleus, then we need to consider the subatomic particles that are inside of the nucleus, which we know are both protons and neutrons as well. The mass number is going to be the total number of protons and neutrons found in the nucleus. Once again, let's take a look at our example down below. We already know the number of protons, and so if we count the number of neutrons, the number of gray circles here in the nucleus, what you'll count is that there are a total of 6. So, to calculate the mass number, all we need to do is total up the two. We have 6p+6neutrons=12, and so this is going to be the mass number that we just defined up above here.
Last but not least, what we have here is the atomic mass, which is also sometimes referred to as the atomic weight.
The atomic mass or atomic weight sounds kind of similar to this mass number idea, and really they are very similar. However, there's one big difference, and this is the idea that the atomic mass or atomic weight, instead of being the mass of the nucleus of 1 atom, it's actually going to be an average total mass of all of the atoms of an element. It is an average, whereas the mass number is not an average; it's the mass of just one atom. Now, in your textbooks, you'll see a periodic table view that looks somewhat like this for the elements. The first number you'll see here is 12.011. This number here is what we refer to as the atomic mass or atomic weight that we just talked about, which is once again an average total mass of all of the atoms of an element, which is why it looks like a strange number here with the 0.011. We'll be able to understand this idea of atomic mass or atomic weight much better later in our course once we start talking about isotopes.
You'll also note that the atomic number tells us the total number of protons in the nucleus, which we know is 6 here for the carbon atom. You'll also note that the chemical symbol is always going to be shown here. For carbon, the chemical symbol is C, and the element name is usually provided as well which is carbon. This here concludes our introduction to these atomic properties of atomic number, mass number, and atomic mass or atomic weight.
We'll be able to get some practice applying these concepts moving forward in our course, so I'll see you all in our next video.