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 discuss three 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 quite simply; it's a straightforward idea. All it is is the total number of protons in the nucleus of an atom. So all you need to do to get the atomic number is count up the total number of protons, and that's it. The atomic number or the total number of protons defines each element. If we change the total number of protons in the nucleus of an atom, then we change the element it falls under. However, changing other subatomic particles like neutrons or electrons does not change the element. Thus, only changing the number of protons or the atomic number will change the element, and that's why the atomic number defines each element. So let's take a look at our example below to clear some of this up.

Here we're examining the atomic properties of a carbon atom, specifically this carbon atom shown here. 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 here. What we'll see is that there are a total of 6 protons in the nucleus, which means the atomic number of this atom is 6. The protons are shown here in red, and by counting the red circles, we find there are six of them, which is why the atomic number is 6. If we were to add a seventh proton, then we would be changing the element, and it would no longer be carbon but rather nitrogen. Adding another neutron or another electron, which revolves around the nucleus, would still leave it as a carbon atom. Therefore, the number of protons in the nucleus defines the element.

Moving on, the next property is the mass number, which is also straightforward. It's the mass of the nucleus of a single atom. To determine the mass number, we consider the subatomic particles inside the nucleus, which include both protons and neutrons. The mass number is therefore the total number of protons and neutrons found in the nucleus. For example, if we know the number of protons and count the neutrons in the nucleus, what you'll find is that there are also six neutrons. To get the mass number, all we do is add up the two: 6 protons plus 6 neutrons give us a mass number of 12.

The last property we'll discuss is the atomic mass, sometimes called the atomic weight. The atomic mass is remarkably similar to the mass number; however, the key difference is that the atomic mass is an average total mass of all the atoms of an element, whereas the mass number is the mass of just one atom. If you look at a periodic table, you might notice a number like 12.011 for carbon. This number represents the atomic mass, which is the average total mass of all carbon atoms, thus the .011 indicating a decimal value. The atomic mass is very close to the mass number but differs because it is an average. This idea will become clearer when we discuss isotopes later in the course. The atomic number, shown as 6 for carbon, indicates the total number of protons, and the chemical symbol for carbon is 'C'.

This concludes our introduction to these atomic properties of atomic number, mass number, and atomic mass or weight. We'll be able to get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.