Physics 2000 Science Trek Elements as Atoms

Electron Configurations Continued

Take a look at the elements beyond lithium and see what you can discover.

Let's see...the fourth element, beryllium (Be), has a second electron in the higher energy level, which means that level now has both a spin up and a spin down. So the next element should begin a third energy level--is that right?

See for yourself. Try clicking on boron (B), the fifth element--you know, the one Bruce Willis was so excited about.

Hey, what's going on? The fifth electron has a slightly higher energy than the other yellow ones, but it's not directly above them; it's in that column labeled "p."

Ah. Do you have any ideas about what might be happening?

Well...my best guess is that the colored rows, pink and yellow, represent the main energy levels, and s, p, and d are like smaller sublevels of them.

Very good. So what do you think is going to happen as you keep going along that row of the periodic table?

Hmm...carbon (C) has a second electron in the p column, so now s and p in the yellow row each have a spin up and a spin down. The next electron must start a whole new energy level, or maybe it goes into the d column, if that's the next higher sublevel.

Sounds very logical...but now look at nitrogen (N).

Hey, the seventh electron went into the p column too! How can there be three with the same energy?

It gets worse. Go on.

Oxygen (O), fluorine (F), neon (Ne)--more electrons just keep getting stuffed into that same state. What happened to the exclusion principle? This makes no sense at all!

It makes perfect sense, once you know the rules.