The repeating nature of the electron configuration or electron structure is shown here also, this time with emphasis on the orbitals. For future reference, note that the atomic size trends (discussed later in this lesson) are also apparent in this diagram.

If you take a look at the electron configurations that are shown there, hydrogen with its 1s1 shows the 1s orbital. Then for helium, 1s2, the 1s orbital is also shown. It is a little bit darker to indicate that there are two electrons in it.

Then the third electron goes into the 2s1 and this is shown with lithium. Notice that the 1s orbital is shown in the center and then the 2s orbital is shown around it in the lighter color and larger. With beryllium there are two electrons in the 2s orbital.

With boron if you look closely, you can see the p orbital that has the fifth electron in it. With carbon you can see that there are two of the p orbitals. With nitrogen you can see that there are three of the p orbitals shown. With oxygen there are still the same number of orbitals, but there are four p electrons. There are more and more electrons as you go from oxygen to fluorine to neon. Thus the diagrams get darker to show the higher concentration of electrons.

Then with sodium you have to start working with another s orbital and that is shown in yellow here. Magnesium shows another electron in that s orbital.

With aluminum, silicon, and phosphorus, you can see the additional p orbitals in the third energy level showing up there. Then the concentration of electrons gets more intense and thus the color gets darker and you go to sulfur, chlorine, and argon.

Again with one more electron after argon, you need to start another energy level and that is shown as the 4s energy sublevel with potassium and also the same with calcium.

This particular progression of elements leaves off after Ca because that is where you start getting into the "d" orbitals which become much more difficult to draw. So with this diagram you can see the progression of additional electrons resulting in additional orbitals and also the orientation and build-up of the orbitals that are being used. You can also see how that relates to the arrangement of the periodic table.

E-mail instructor: Eden Francis Science Department 19600 South Molalla Avenue Oregon City, OR 97045 (503) 594-3352 TDD (503) 650-6649

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