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Home School Life Journal ........... Ceramics by Katie Bergenholtz
"Let us strive to make each moment beautiful."
Saint Francis DeSales

Chemistry: The Aufbau and The Pauli Principles

Continuing from the last chemistry post, I have found it so much easier to explain the Pauli Principle and the Aufbau Principle by using a visual model of the atom.

The electron configuration of Cl (Chlorine) [Ne] 3s2,3p5.

This manipulative is part of the Friendly Chemistry program. It is a plastic coated page that fits snugly inside a baking pan. Small magnet discs in two colors are used to represent the electrons, one color representing the electrons moving clockwise, and the other color representing the electrons that move counter-clockwise.

I have made similar manipulatives with posterboard before in a co-op class, however, with success. Once I hot glue-gunned tiny bathroom cups to the circles and then used small pom-poms in two colors to be placed in the cups to represent the electrons, although the even smaller cups found in some restaurants or fast-food places would work even better, if you can get enough of them.

I have also just made the circles on posterboard or large sheets of construction paper and used math counters or glass discs that are sometimes used with planters, which can be found in the garden section or sometimes in dollar stores, without the cups. You just have to be careful that the paper doesn't get knocked.

Whatever method you use, you just start with the nucleus of the atom at the bottom and using the Aufbau principle, make the appropriate circles representing the possible orbitals to be filled.

Aufbau principle: The orbitals are filled in the order 1s, 2s,2p,3s,3p,4s,3d,4p,5s,4d, 5p, 6s, 4f, 5d, 6p, and so on.

The electron configuration of C (Carbon) [He] 2s2, 2p2.

Once you get your board set up, your student can begin filling the circles, using the Pauli principle. Don't forget that when your student gets to atoms which need to fill the x, y and z orbitals of the 2p, for example, that he must add the first electron to either the x, y or z orbital and then whichever one he chooses, the other two p orbitals must be filled before adding a second electron to those set of three orbitals.

The Pauli principle: Each orbital can hold at most hold two electrons.

We also looked at the fact that each atom has the configuration of the nearest previous noble gas atom, which is in brackets, and whatever valence electrons it has, which is listed after.

For example, in this visualization, this is the configuration for of Cl (Chlorine) is its nearest previous noble gas atom, which is [Ne] or Neon and then also has the valence electrons of 3s2,3p5. Once your student can easily place these electrons, then you can easily teach them about the differences between ionic and covalent bonding.


  1. Wow, it's been so many years since I had to do that. I remember loving to fill orbitals back when I was in chemistry and figuring it out. Now, ahem years later, I'm reading it and knowing I should know what it means, but not remembering all the fine details.

  2. It will come back to you! If you following along with your kids, it will come back easily enough. There was a lot of new stuff that came out about atoms between my high school days and now, so some of it was entirely new to me. My kids ask me if there were electric lights then. :)

  3. Visiting from Science Sunday and am embarrassed to admit that I have no idea what you are talking about.
    I didn't take chemistry. Looks like I need to hang around here so I can learn a thing or two.

  4. One of these days we're going to have to delve a little deeper into science - there's so much to know!

  5. I took chemistry, but I don't remember that at all.

  6. I am sorry, perhaps I needed a post that went into the different types of orbitals first. I will try to post one about that this week. It is surprising quickly the chemistry material changes. There were some changes from when Katie took chemistry two or three years ago and the new book I bought this year.

  7. I took organic chemistry in high school and I have no idea! Maybe this is why I didn't major in chemistry in college! I will have to come back here when we get to that part.

  8. I am sorry I confused everyone. I have inserted another post, that will hopefully clarify everything. Let me know if I am still unlear.

  9. Oh no! I don't think your post was confusing at all. It was just unfamiliar to me. Chemistry was not my favorite so I may have played hooky or doodling when this was taught. It's a brilliant post!


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