# Electron Configurations in the s, p & d Orbitals

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• 0:01 Electron Notation and Orbitals
• 0:58 s Orbital
• 2:26 p Orbital
• 3:27 On the Table
• 4:18 d Orbital
• 5:52 Lesson Summary

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Lesson Transcript
Instructor: Deborah Ryan
Getting confused by long lists that start with 1s and seem to go on forever? Don't worry, this lesson on electron configuration will help you understand how to describe electron placement in no time.

## Electron Configuration and Orbitals

The periodic table does so much more than just tell us the atomic number of an atom. In fact, we can use it to help us figure out how different substances will react if given certain circumstances. For example, elements in the same column often bond similarly. We see this most clearly to the far right with the noble gases, which don't bond well with others. However, knowing what electrons are free in a given atom can help us figure out how the rest of the elements will react to one another.

An easy way to figure out how elements bond is through electron configuration, a system of stating how many electrons are present in each orbital of an atom. Remember that an orbital is the orbit that electrons can take around the nucleus. In this lesson, we're going to learn how to use electron configuration to describe the first thirty-six atoms on the periodic table so that you'll be comfortable using it later on to describe larger atoms.

## S Orbital

The closest orbitals to the nucleus are the s orbitals. The s orbitals are also the smallest, and can only have two orbiting electrons. Therefore, all the electrons in both hydrogen and helium fit in the first orbital. We write this as 1s^1 for hydrogen, since it is in the first s orbital and has one electron. Meanwhile, we write it as 1s^2 for helium, since there are two electrons there.

But there's a catch. The next layer out from the 1s orbital is the 2s orbital. Like all other s orbitals, there is only room for two electrons. So what does that mean for lithium which has three electrons? The first orbital, 1s, is completely full. As such, we write 1s^2. But we're not done yet. We also have another electron, so that means we step up in energy level. Because we're still in the 2s orbital, we write 2s^1, since there is only one electron there. However, we still put the 1s^2 there, so lithium has an electron configuration of 1s^2 2s^1.

But wait, what about energy levels? Each coefficient represents a step up in energy level. Think about it like this. Electrons don't have to work so hard to stay close to the nucleus, but they have to move really fast in orbit the farther out they go. As such, electrons increase in energy as they get away from the nucleus.

## P Orbital

You can probably guess by now that beryllium, with four electrons, has an electron configuration of 1s^2 2s^2. But what about boron with five electrons? For that, we use a completely different set of orbitals, the p orbitals. P orbitals are groups of three orbitals, which means that they can have six electrons total. You write them the same as s orbitals, but never with a 1. That's because the energy level for 1 is too low for p orbitals. For example, that would mean that boron would have an electron configuration of 1s^2 2s^2 2p^1. Carbon would be 1s^2 2s^2 2p^2, with an additional electron, and oxygen would be 1s^2 2s^2 2p^4, since it has two more electrons than carbon. The third energy level also has only s and p orbitals, so that means that you've got all the tools you need to go up to argon.

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