## Chem – Energy Levels

What sections should I know before attempting to learn this section?

What are energy levels?

Now that we have talked about the orbitals we can start to talk about how they are related to more complex subjects like energy levels. Energy levels refer to the distance of electrons from the nucleus. The further the electron is from nucleus the greater energy it has. Just like the higher you raise a book from the ground the greater energy it has. In both cases, if you allow the electron or the book to fall, the energy will be released. The electron with release the energy in the form of light and the book will release the energy in the form of the loud crashing sound. The energy levels are depicted on the periodic table and relate to the different orbitals discussed above. They ROUGHLY follow the periods of the periodic table but it depends on what type of orbital you are viewing. The best way to understand the energy levels is to compare the energy level diagram with the energy levels on the periodic table.  I demonstrate this in the video below.

VIDEO Energy levels

For the energy level diagram, the numbers in front of the different orbital types are the indications of the energy levels. You can see that the first energy level only has the S orbital. However, the second energy level has both the S and P orbitals. If we keep going, the third energy level has the S, P, and D orbitals. So, each time we move down an energy level we add a new orbital type. The picture I have above is not complete. Theoretically you could go on forever. However, I show it up to the 5th energy level because most students do not need to know beyond that. Also, at the 5th energy level it starts to get into theoretical orbitals like the G orbital that don’t appear on the periodic table. All you have to know about the theoretical orbitals is that they start in the fifth energy level at G and then go in alphabetical order (G, H, I…) as you continue down the energy level diagram. Questions about energy levels often revolve around how many electrons each of them can hold.

Examples: How many electrons can each of these energy levels hold?

 First energy level 2 Third energy level 18

VIDEO Counting Electrons in Energy Levels Demonstrated Example 1: How many electrons are held in the first, second, and third energy levels total? Try this link to a periodic table with the energy levels on it as you go through this problem.

Step 1:

What type of orbitals are in the 1st energy level?

Step 2:

How many electrons do the S orbitals hold?

Step 3:

So how many electrons are in 1st energy level?

Step 4:

What type of orbitals are in the 2nd energy level?

Step 5:

How many electrons do the P orbitals hold?

Step 6:

So how many electrons are in the 2nd energy level?

Answer: S + P = Total …… 2 + 6 = 8

Step 7:

What type of orbitals are in the 3rd energy level?

Step 8:

How many electrons do the D orbitals hold?

Step 9:

So how many electrons in the 3rd energy level?

Answer: S + P + D = Total …… 2 + 6 + 10 = 18

Step 10:

How many electrons in the first 3 energy levels?

Answer: First + Second + Third = Total …… 2 + 8 + 18 = 28

PRACTICE PROBLEMS: How many electrons can each of these energy levels hold? Try to use a regular periodic table when you answer these.  If the regular periodic table is not enough try this link to a periodic table with the energy levels on it as you go through these problems.

 Second energy level 8 Fourth energy level 32  