confused about quantum numbers

kats · Sep 16, 2003

Ok, maybe it would help to ask more specific questions? I have been reading some web sites and my "Chemistry for Dummies" book. I understand how to get the l, m, and s numbers, but am still confused with determining the number for n. Is it just one more than the highest orbital number? Also, how do you know which number goes to which element? For instance, our teacher said that H is (1,0,0,1/2) and He is (1,0,0,-1/2). Is it just that the positive number is always first or is it something else? Thanks in advance to any brave souls who might offer to help.

LeesieBug · Sep 17, 2003

n, beleive it or not, is just the Period .... n can be equal to 1-7. So, to determine n, look at the periodic table and locate the row the element is in. (the key to understanding ALL the quantum numbers stuff lies in figuring out the periodic table).

For H:

n= 1 (it is in period 1)

l= 0 ml=0 ms =1/2

To determine l values: If you look at the periodic table, H is in group IA.....the representative elements in groups IA and IIA are s's. s's have an l value of 0 ..that's just something you can memorize. He, although it is in a group with the p's, is the oddball because it is an s.

Groups IIIA, IVA, VA, VIA,and VIIA are p's. p's have an l value of 1.

d's are the transition elements, the B's groups at the center of the table, and have an l value of 2.

the f's are the two colums at the bottom of the table, the inner-transition elements. Those element have a l value of 3

So to determine l, find thethe location of the element, determine if it is a s,p,d,or f. You just have to remebmber that the l values are s=o

p=1

d=2

f=3

So if you want to know the l value for Carbon, you find carbon, determine that it is a "p" by its position, and know that p's have an l value of 1. So carbon's l value is 1.

To DETERMINE ml values: if you are dealing with an "s", ml is 0

if a "p", ml is -1,0,1

if it is a "d", m is -2,-1,0,1,2

if an "f", m= -3,-2,-1,0,1,2,3

Hopefully I didn't confuse you more! I think this can be one of the most confusing things in chemistry...but hang in there..eventually a light bulb goes off and you see the relationship in all this nonsense.

Try looking for high school, or elementary school chemistry web sites. When I had chem I did that A LOT because they spoke in plain english....GOod luck!

gwenith, BSN, RN · Sep 17, 2003

I am unsure of whether you want an explanation of chemistry or Quantum mechanics.

If your teacher has wandered off into the weird and wonderful world of quantum mechanics then here is a link

http://www.newscientist.com/hottopics/quantum/

kats · Sep 17, 2003

LeesieBug, thank you so much for replying. You did help. As for the "n" number, our teacher had said that it could be any number from one to infinity. That was what was confusing me because I thought he had also said it would be the number of the period. It didn't seem as though it could be both. Just to clarify, you are talking about periods 1-7a and b, right? What about the noble gases though? They have 8 at the top. I still have a couple of other questions too. When you are talking about the s, p, d, and f you are talking about the last letter in the electron configuration, right? Also, I am not entirely sure how to determine if an element is positive or negative charged. Is that on the periodic table? One more thing, when determining the "m" number, how do you know which number out of the possible choices goes to which element? I think that is all I am confused about for now. Again, thanks a lot for your help. I will also try to look for some more web sites too.

kats · Sep 17, 2003

Ok, never mind about the question regarding the period numbers. I got them mixed up with the families/ groups for a second.

marilynmom, LPN, NP · Sep 17, 2003

Just remember that the periodic table is set up to make sense, even if you dont see that now. Things are where they are at for a reason and a lot of it is just plain memorization.

Also after awhile things will start to come together more. I know when I took Chem we would all be sooo confused but then after a week or whatever it started to make sense. Just dont study so hard that you get so stressed out and have to much info in your head. Sometimes I would have to just put my book down and go to bed, the next morning I would wake up and things would make sense!

Good luck!

Marilyn

passing thru · Sep 17, 2003

The thing I remember the most is that the professor said a young Englishman figured out--"created" the periodic table.

And , then, they drafted him into the military during WW I , and he was killed !!

After that, the English decided to exempt their brightest minds from military service.

................................................................ duh !.....................

LeesieBug · Sep 17, 2003

Might want to talk to the instructor about spin.... I wrote that down wrong earlier, I noticed. ms, or spin, has to do with how many electrons are in the valance shell, but I forget EXACTLY how to determine it correctly.

The instructor probably said that n can go through infinity because, potentially, it can. We just use the 1-7 for our purposes, going by the periodic table of elements. I remember our instructor saying something to that effect, but I don't remember details.

As far as ml values, you just look and see where the element is. ml is dependent on the l value. If you have an "f", the l value is 3. If l is 3, then ml is -3,-2,-1,0,1,2,3. We never had to isolate one value, maybe you guys are going into more depth than that. In everything we learned, and I read, you just have to state the ml values in relation to what l is.

kats · Sep 18, 2003

I went to class early yesterday and talked with my teacher. The biggest thing I was misunderstanding was somehow I had it in my head that there was one quantum number per element as opposed to one for each electron. Since that number gets quite high for a lot of elements, my teacher said that we won't have to actually make a list of them. Instead, we have to just be able to explain the different parts of the number, how to figure them out, and what they represent. Thanks again for all of your help.