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Tips on Electron Configuration - Concept

Teacher/Instructor Kendal Orenstein
Kendal Orenstein

Rutger's University
M.Ed., Columbia Teachers College

Kendal founded an academic coaching company in Washington D.C. and teaches in local area schools. In her spare time she loves to explore new places.

Tips on ensuring a top grade on your electron configuration assessment. Below, I have Aufbau's Principle, and this is a chart that you've probably seen in class. It helps you identify which orbitals have the lowest energy, and which orbitals have the highest energy. You know electrons. As you know this should be obvious for your electrons, and the one that's orbital first. Let me make this so it's easy to see. I just follow the arrow in order.

Notice, I also added a number of orbitals you probably haven't seen before. Each principal energy level has the same number of sub-levels as it does principal energy levels. So the 1s for example has one sub-level. 2, the second principal energy level has two sub-levels; the s and the p. The third principal energy level has three sub-levels; s, p and d, and so on and so forth. But some of them are theoretical, and some of them are actual. Well, they're all theoretical, but some of them we haven't seem them exist before.

In the periodic table, this is where the electrons stop, meaning we don't have any other electrons before this. So we stop here. Here is where our periodic table stops for now. Everything over here is on our periodic table. Everything over here hasn't been quite discovered yet. It's all theoretical, but they counts when asked questions about them. What the heck do I mean when I say that?

Let's go to some commonly missed questions that you might see in your test that I find that students of all levels miss quite often. The first one is how many electrons can fit in the third principal energy level? I'm not necessarily saying just the third. It's any. We're going to call this n. In n energy principal energy level. Let's just put 3 to help you understand what I'm talking about.

Here is our third principal energy level. We have an an s which has 2 electrons can fit in there. One orbital, 2 electrons. We have a p, 6electrons which means three orbitals can fit there in the p. We have a d which has 10 electrons in other words 5 orbitals.

So the total number of electrons, that can fit in the third principal energy level, are 2 plus 6, is 8 plus 10 is 18 electrons. Total number of orbitals is 1 plus 3 is 4, plus 5 is 9. An easier way to do this, is to say orbitals is n². So in this case the third one, it's 9. 3² is 9. Electrons is just double that, so it's 2n².

Let's say the n was 7, so we got the 7th principal energy level. Well, number of orbitals in n² which is 49. It does have 49 orbitals. Look at all these orbitals that they have. This is also in theory, but they count. Number of electrons is 49 times 2 which is 98 electrons.

So make sure that you know this. This is a commonly missed question, because students forget about these orbitals over here in the crossed out spot. Don't forget about these. They are rare.

Next question is how many electrons fit in a single 5p orbital? Well, like I mentioned before is it 2n²? This is a single 5p orbital. This is for 5th energy level. So this is not right. 3 electrons? There are 3 orbitals in a sub-level of p, but that doesn't answer the question.

How about 6? No, because we have the word single here. 6 is for total electrons in p sublevel. The answer is 2, don't miss this word. This is a very common question I've seen on so many teacher's test all over the country. Kids always get this wrong. Make sure you are a good test taker, and read the questions thoroughly. Do not miss this simple question, because everybody can answer this, and that will lose points. I don't want you to do that.

Lastly, which orbital has the highest amount of energy? A lot of times people pick 6s because the principal energy level is 6. Not the case. Looking at this, the Aufbau's diagram we mentioned up here, our 6s is down here. 5p has less energy than the 6s. So far it goes 5p is the lowest, and 6s is the second lowest. After 6s, comes 4s. So this chart is really helpful in identifying a lot of different things, and the way electrons fall into atoms.

Hopefully this helped you not miss this silly little questions that come up. So you want to get as many points as you possibly can on these tests. So you don't want to miss them over dumb little things. So hope that helped.