Atomic Number, Mass Number, and Net Charge

here's a diagram of an atom, it's not perfectly accurate, but for what we need now it will work fine, so in this lesson we'll look at the characteristics that we can use to describe atoms like this, you know, if anyone asked. To describe a person, you are likely to use characteristics like the color of their hair, the color of their eyes, their height, etc., just like that, there are characteristics that we can use to describe atoms, the first of these characteristics and Perhaps the most important thing is the

atomic

number

. The

atomic

number

is often abbreviated with a capital letter Z and the atomic number is the number of protons in the nucleus of an atom.

In my diagram here I'm using these red circles to represent protons, so we have 1 2 three protons in this atom, so the atomic number will be three for this atom. Here the atomic number is particularly important because the number of protons in an atom tells us what type of atom it is and by that I mean if a carbon atom is an oxygen atom is a sodium atom we're going to talk more about that in the video about Isotopes so you don't have to worry about that for now the next important characteristic that we can use when describing atoms is the

mass

number often abbreviated with a capital letter a here the

mass

number is the number of protons plus the number of neutrons in the nucleus of an atom people always get confused with the mass number here's why atomic number is the number of protons so everyone always wants The mass number is the number of neutrons but it's not, is a number of protons and neutrons.

In fact, there's not really a name for the number of neutrons, just the number of neutrons in an atom, we just don't use it that often, so anyway. mass number we want to count all of these together 1 2 3 4 5 6 7 the mass number of our atom here will be seven now finally the third characteristic that we are going to talk about here is probably the most complex and it is called net

charge

I don't have a good way to define net

charge

. I mean, I don't have a good definition, so what I'm going to say here is how protons and electrons balance each other, let's talk a little more about this charge it's about how protons and electrons balance each other, so protons, as you know, have a positive charge and electrons have a negative charge, that means that if we have the same number of protons and electrons in an atom like the one I have here three protons and three electrons I'm not drawing the neutrons here because we're not worried about them here we have the same amount of protons and electrons they're going to balance each other this minus 3 is going to balance the positive three so we're going to end up with an atom that has a net charge of zero because these two Things balance out and we can call this atom neutral, meaning it has no net charge.

Now, what would happen in an atom where we have four protons and three electrons, we no longer have the same number of electrons and protons, so they cannot fully balance each other. Instead, we have more protons than electrons, so we will have a net positive charge because there will be some of this positive charge on the protons that the electrons will not be able to balance. In this case, we have one more proton than one electron, so this will give us a net charge of plus one, since our atom has a net charge we give it a special name we call it an ion an ion is any atom that has a charge net neutral is what you call it if you have no charge ion is what you call it if you have any charge okay this is where we have one more proton than one electron, what happens in this case?

What would happen if we had five protons and three electrons? In this case the charges are not balanced either, but now I have two more protons than electrons. I have two more protons. which don't balance with these electrons, which means I'm going to have a net charge of two more for these two protons and again this is going to be an ion because it has a charge. Now the opposite can happen. Well, here's an example where an atom has four electrons and three protons, so it now has more electrons and protons. These three protons can only balance three of the electrons, so I have one more electron that doesn't balance, which means this total charge.

It's going to be minus one, that's one more charge of this electron that I have on the proton and if I had a case where I had five electrons, oh, I should have said we call it an ion because it has a fair charge. like this negative charge positive charge it doesn't matter if it has a charge we call it an ion okay anyway we have a case where we have five electrons and three protons now there are two more electrons and protons so I have two negative charges that don't balance each other with the proton, which means I have a net charge of minus 2 and this is also an ion, this is how you can calculate the net charge, so what is the net charge of this atom?

Well we have 1 2 3 four electrons and we have 1 2 3 protons since they are different numbers the protons and electrons will not balance each other we have one more electron than one proton which means we have a net negative charge and Since there is one more electron than one proton, this atom will have a net charge of minus1, so now that we've talked about these three characteristics that you can use to describe an atom, let's watch the practice problem video so you can review this and a little more depth and try a lot of examples