Recording #38

Hi everybody, this is Mr short today, we're going to be learning about electron configurations or set another way how electrons are arranged inside an atom to put this into perspective. Remember, we just got done with section 1.1 where we learned about an introduction to atomic structure. We learned about things like where the protons and neutrons are at that. The electrons are outside the nucleus. And we learned about some experiments by Thompson and Rutherford that led to our understanding.

Of modern atomic structure today, we've got four objectives, and these objectives are to write complete electron configurations. And again, electron configurations show the arrangement of electrons inside atoms. We'll also take a look at the structure and organization of the periodic table in particular we're going to take a look at four sections or blocks on the periodic table called the s p, d and f, blocks we'll learn about a shortcut called an abbreviated noble gas electron configuration, and we'll.

Also address the question, what happens when atoms turn into ions? Now first spent are called blocks on the periodic table. These are different sections on the periodic table, and they're important for understanding electron configuration. So what do they mean spent refer to sublevels within? What are called a Princeton, quantum energy level.

These sublevels are located here in the s block in the p block over here in the d block over here and the f block over here. So as we go. Through in this section, I think you're going to see a lot of similarities between structure and organization of the periodic table and the arrangement of electrons inside atoms. Okay, the other thing that we can get from this particular picture right here is it shows what order we write the electron electrons in the electron configuration. So for example, we would start out at the top with 1s here and here, and then we would go down to 2s, and then we would go across to 2p.

And then we would go down. To 3s across to 3p down to 4s to 3d, I know that seems like it's out of order, but that's the way that it goes and then up to 4p and that's all that we're going to do in this class is up to 4p. So we should start with the question, how many electrons can each sublevel? Hold the s sublevel holds two electrons. And I want to go back to the previous slide and point out that the s block has two columns inside the s block. Likewise, the p sublevel can hold six electrons.

And the p block has six vertical. Columns one two, three, four, five, six. So remember, s, the s block is here.

The s, sublevel holds two. Electrons p block is right here. P, sublevel holds six electrons. The d block is here. It holds ten. Electrons f block is here. F. Sublevel can hold 14 electrons.

So 2, 6, 10 and 14. Now you'll write. So many of these that you end up memorizing, these numbers, but just notice that it's a sequence 2 plus 4 is 6 6, plus 4 is 10 10, plus 4 is 14.

All right. Let's. Take a look at an example of an electron configuration. And I've written the order of electron configuration right up here, if we think about the element arsenic in its neutral, state has 33 protons.

And in its neutral state, it would also have 33 electrons. So we want to figure out how to represent the electron configuration for neutral arsenic, which has 33 electrons. This would be the neutral electron configuration for arsenic, which has 33 electrons. Notice that we start at the beginning of the electron configuration 1s. And we fill that sublevel. Up completely now, remember the s sublevel can hold two electrons.

Then we write the next sublevel, which is 2s fill it up completely next sublevel, which is 2p. We fill it up completely. The p sublevel holds 6, electrons, 3s, 3p, 4s. And then remember after 4s does come 3d and a d sublevel can hold 10 electrons so 10. And if we stop right here, and we add up these exponents up to and including 3d 10, the exponents we're going to find they represent the electrons so 2, plus 2, plus 6, that adds up to 10. Then 2. Plus 6, plus 2, that's, another 10.

So right here, we've got 10 here. We've got 10, that's, 20., here's, 10. So that adds up to 30. And then we need to stop at 4p3 because the sum of these exponents now adds up to 33.

And we want to represent 33 electrons for neutral. Arsenic, here's, another example, let's see, if we can do this, we've written a complete electron configuration below 1s2, 2s2 2p6. So the question is, how many electrons does this neutral element have? And what is the symbol for this neutral element? Go. Ahead and hit pause and figure that out.

So remember the sum of the exponents adds up to the number of electrons. And since this is neutral, the number of electrons would also equal the number of protons since the exponents add up to 10. This must have 10 electrons in its neutral state and the element that has 10 electrons in its neutral. State is neon. Okay, neon is the element that has 10 protons and 10.

Electrons, right? Let's. Take a look at something called a noble gas electron configuration or an. Abbreviated noble gas electron configuration. First, we need to know where the noble gases are located on the periodic table. The noble gases are on the far right-hand side of the periodic table, they're in so-called column, eight or main group, eight, it starts with helium and ends with radon over here. So it goes helium.

Neon, argon, krypton, xenon and radon. Those are the noble gases we're going to use those as a shortcut, and we're going to see why? Okay. So noble gas electron configurations.

The noble gases are listed right there on the far right-hand side of the periodic table. And what we might notice is that each one is at the very end of that particular row it's on the far right-hand side of each horizontal row on the periodic table, noble gas configurations, take advantage of this by condensing, what you have to write something that looks like this. So let's, take a look all right?

Helium is element. Number two in its neutral state. It would have two protons and two electrons and its. Electron configuration would be 1s2, but we can abbreviate this, and we can just put bracket helium and that's. The way that we say this bracket helium, bracket.

Helium means 1s2 here's, another example, so let's say that we're dealing with carbon. Carbon is not a noble gas. But carbon in its neutral state has 6 protons and therefore 6 electrons its complete electron configuration would be 1s2 2s2 2p2 that adds up to 6. And take a look because carbon has this 1s2 in it. And we know that 1s2 is equal to.

Bracket helium, we can do a little substitution here. And we can say that the noble gas configuration for carbon is bracket. Helium 2s2, 2p2, see how all we did.

There is a little of substitution. We substituted bracket helium for 1s2 to get bracket helium, 2s2, 2p2 by the way that should be a superscript right there all right. Let's. Take a look at another example, all right, here's an example for arsenic. We took a look at arsenic earlier, and we saw that arsenic in its neutral state has 33 electrons and. This would be the complete electron configuration for arsenic.

Remember, the sum of the exponents has to add up to the total number of electrons in this particular substance. And those exponents add up to 33. Okay, notice this part in yellow, though it's the same as argon's configuration and argon is one of those group 8 noble gases. Argon's configuration is 1s2, 2s2, 2p6, 3s2 3p6.

So the noble configuration will start with the gas that's in the row before it. So for this up here, we can do some. Substitution, and we can say that all of this in yellow equals bracket argon, and then we just need to continue beyond it 4s2 3d10, 4p3. So remember bracket argon equals 18 electrons, let's, confirm that 2 2 and 6 is 10 plus another 2. And another 6 adds up to 18. So this means the first 18 electrons, there's, 20, 30, 33 and that's how we can use this shortcut with an abbreviated noble gas electron configuration to represent the electron configuration for arsenic.

Okay? And it does cut down on a lot of. Writing, and that is a good thing all right.

Let's. Take a look at a couple more examples up top. I've put two complete electron configurations for two of the smaller noble gases.

And I've written their very simple noble gas configuration and then down here I've written. Okay, sodium in its neutral. State has 11 electrons. So 2 2, 6 and 1 adds up to 11.

Since neon ends in this configuration 2p6. We can substitute bracket neon to mean, the first 10 electrons, and then we just continue on from there, but. Take a look when sodium turns into sodium ion, it takes a positive charge. And the way that it takes a positive charge is by losing this 3s 1 electron. So now this would have 10 electrons, and it would be 1s2, 2s2 2p6. And that is the configuration for neon.

So we can just abbreviate sodium ion as bracket neon. If you take a look down here, chlorine in its neutral state would have 17. Electrons 2 2, 6 and 5 adds up to 17. What we can do is we can use bracket neon to represent the first 10 electrons and. Then continue on from there, 3s2 3p5. So remember, this is 10 there's, 12, there's, 17, that's.

How many we want when chlorine turns into chloride ion it gains an electron? So it no longer has 17 electrons. Now it has 18 electrons. And that new electron is this 3p6 electron right here.

So take a look chloride ion would now have 2 2, 6, 2 and 6. That adds up to 18 electrons. So I want you to take a minute. And I want you to predict the abbreviated noble gas configuration for chloride ion that's, right chloride. Ion would have the abbreviated configuration bracket argon because remember argon is the noble gas that has 18 electrons.

So in general, I want us to summarize what happens when an atom turns into an ion when an atom turns into an ion, the ion will look like a close, is it alkali metal? Alkaline earth metal, halogen or noble gas, pause and make a prediction about what that is that's right? The answer is noble gas. Okay. So when an atom turns into an ion, it will look like a close noble gas.

Now, what I mean. By look like is that it has the same configuration as a closed noble gas here or here. But it does not have the same number of protons as a closed noble gas all right. So let's review, real quick. On the left-hand side, I've got the objectives and on the right-hand side, I've got some examples. So we took a look at how to write things like electron configurations for magnesium.

For example, since magnesium in its neutral state has 12 electrons its complete electron configuration would be 1s2, 2s2, 2p6, 3s2. Because of the sum of the exponents adds up to 12. Its abbreviated noble gas electron configuration would look like this. We can use bracket neon to mean. The first 10 electrons ending in 2p6, until we can say that it's bracket neon, 3s2. We also took a look at the structure and organization of the periodic table. In particular, we said that these are this is called the s block.

Right here. It's got two columns. This is the p block right here. It's got six columns.

D block has 10 columns and f block has 14. Columns and that relates to the maximum number of electrons that can be held in each sublevel. We also took a look at what happens when an atom turns into an ion. And we said, it will look like a closed noble gas here.

We've got an example down here. When neutral magnesium loses these two electrons to turn into magnesium ion it now has the same electron configuration as neon. So we can say bracket neon is the new electron configuration. All right. Thanks. A lot.

Guys have a great day.