My Great-Great-Great-Great-Great-Great Grampappy just died, and he left me a mansion. I’m excited… umm, as well as mournful and emotionally destroyed… (wink). There’s still some paperwork to fill out before I can move in, but I decided to check out the place anyway. You know, since it’s technically mine anyway.
My sister and I took a drive out to see the house – magnificent. The architecture astounded me; it’s shaped like an upside-down pyramid. It was so beautiful, in fact, that my sister couldn’t help herself from darting from the car and through the front door. Two hours later, I had NO IDEA where she went. She called me on my cell phone to ask me how to get where I was. It took somewhere in the realm of two weeks for us to find each other, but I am happy to announce that we are both still alive and reunited.
You know, it’s too bad my sis and I didn’t know back then what I now know about quantum numbers. Why? Because quantum numbers are a system of identifying the location of an electron within an atom (or a sister within a mansion). Allow me to explain:
There are four quantum numbers that you really have to worry about (there are technically more, but in general chemistry, you only need to be familiar with these): N, L, Ml, and Ms.
Principal Quantum Number (
n)
So, the first thing I would need to know if i wanted to locate my sister within the house would be what floor she was on. This would be especially helpful because I could eliminate a HUGE percentage of the house from the search if I could narrow the possibilities to a single story on the mansion.
As far as chemistry is concerned, the tool here is the principal quantum number, or “n” for short. The principal quantum number tells you which energy level that an electron can be found in an atom. Think about it like this: if n=3 for an electron, that electron is on the 3rd floor of the atom.
Azimuthal [Angular Momentum] Quantum Number ( l )
Well, now let’s assume that she’s on the third floor (n=3), but where on the third floor? There are HUNDREDS OF ROOMS up there!! It’s too bad there isn’t a way to tell what room she’s in…
Que chemistry again. The “Azimuthal” or “Angular Momentum” quantum number does just that. This number, represented usually by a lowercase L, tells you which shaped orbital the electron of interest is residing in. There are plenty of differently shaped orbitals, but you only need to know these:
- l=0, S-shaped orbital
- l=1, P-shaped orbital
- l=2, D-shaped orbital
- l=3, F-Shaped orbital
The shapes of the orbitals aren’t actually the same shapes as the letters S, P, D, and F. Those letters represent the shapes of the orbitals, which is a topic for another post.
But, think of the azimuthal quantum number as representing the room that the electron can be found in. For example: if n=2 and l=1, we know that the electron is in the second energy level, and it’s somewhere in the P orbital. In terms of my sister, she’s on the second floor and in the kitchen, as opposed to the second floor bathroom.
Since the house is shaped like an upside down pyramid, the number of rooms on every floor has to get bigger as you climb upstairs. In fact, it’s just one fewer than the number of the floor itself. So on the 100th floor, there would be 99 rooms! The angular momentum quantum number works just the same. In order to find out what it is, just subtract one from (n).
Magnetic Quantum Number (Ml)
So, now we’re going with sissy being on the second floor (n=2) and in the kitchen (l=1), but now where in the kitchen? It’s a mansion after all, and there is a pantry, a cooking space, and a dishwashing room. She could be in ANY of those places.
The Magnetic Quantum number tells us a little more about where the electron is. It also specifies how many electrons can fit in a certain orbital. Let me explain:
Sissy is in the kitchen, but she could either be in Ml= -1 (the pantry), Ml=0 (the cooking space), or Ml=+1 (the dishwashing room). She told me that she was getting a snack, so I think it’s safe to assume that she’s in the pantry (Ml=-1).
Think of the Magnetic Quantum number like that. It will be found in a range from negative angular momentum to positive angular momentum. Example: If l=5, then Ml can only be between -5 and +5.
This may not make since right away, but it’ll be more clear when you work with electron configurations.
Spin Quantum Number (Ms)
I have no idea how to tie this one in to the upside down pyramid story, so I’ll do my best to explain it in a way that’s easy to understand.
You may already know that no more than two electrons can be in the same subshell (you’ll understand it more in electron configurations)., but you may not know that they have to be spinning in opposite directions.
In order to really understand that, I would have to explain a lot more chemistry than I actually understand… so I would probably confuse you in the process. So just take my word for it.
Because there’s not really any point of reference in the atom, we simply denote the first electron as going one way (+ 1/2) and the other electron is going the other way (- 1/2). It’s really that simple.
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An Article by
Mitchell
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Sidenote:
Hey nerds! This is Grey. I just wanted to throw in a link to a site that I found that gives a visual aid to electron configurations. Many teachers go over electron configurations at the same time as quantum numbers, so I thought this might be helpful.
Best of Luck!
June Poll
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