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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,044

what are pricipal and secondary quantum numbers?

here is a ques i encountered,pls help.:-

If n and l be the principal and secondary quantum numbers respectively,what will be the total number of electrons in a given energy level?

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I also wanted to know for a long time

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,044

i thought someone would have answered it.

by the way this question was in NTSE.

Can you suggest some forums devoted to science?(similar to this forum):)

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I was trying to make a forum but no one joined me: http://guide-to-the-galaxy.co.nf/

Maybe, you can join this one? https://www.facebook.com/groups/Science4fun/

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,044

i am not on facebook.

let me see if I can find one.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 93,600

I came across this while looking for something else.

The integer n in the Bohr model (and other more general models) of the atom which describes the electron shell in which a given electron resides.

The principal quantum is denoted by n and can take the values 1,2,3...

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,917

And if I remember correctly, l can take values 0 to n-1.

*Last edited by anonimnystefy (2013-12-03 05:15:57)*

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,861

hi everyone,

I don't know either but I may know someone* who does.

Trouble is: there's those who think MIF is wonderful and could spend hours here; and there's those who think it's a waste of time (sorry ) and why aren't you outside mowing the grass?

When I asked, she* was vey busy and gave me a curt response. I'll try again when the mood is right.

Bob

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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,044

mif is not wonderful, it is much more than that.

As per my opinion , I haven't seen any forum so enthusiastically devoted to maths and making this subject so interesting.

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^sounds like an Alokananda style compliment.

Did you figure out what quantam numbers are? I suggest you read the Class XI and XII NCERT Chemistry books.

http://www.ncert.nic.in/ncerts/textbook/textbook.htm

By the way, do you have an idea of what is there in the ICSE syllabus for Class X physics?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,861

hi niharika_kumar

I've never really understood quantum mechanics and, having spent a while now researching your question, I get the impression nobody else does either!

Feynman wrote:

"If you think you understand quantum mechanics, you don't understand quantum mechanics

Here's what I think, but it may all be wrong so believe me at your peril:

Electrons are not like miniature planets orbiting a nucleus. And 'shells' don't really exist as there is a non zero probability that an electron could be at any distance from a nucleus.

But let's pretend shells do exist because I cannot finish this without.

Electrons can only be at certain discrete energy levels. That's what 'quantum' means.

The principle quantum number tells you how many energy levels or shells an atom may have. It is given the letter 'n' and n can only be 1, 2, 3 etc.

The secondary quantum number is also known as the angular momentum or azimunthal Q.N. It is denoted by the letter 'l'.

l may take the value 0, 1 2, 3 .... up to n-1.

Letters are also used for these as follows: s=0, p=1, d= 2, f= 3, g= 4, h= 5 etc.

The reason for this choice of letters dates back to the time when scientists were first doing experiments to determine the nature of the atom. Spectra were described as sharp, principal, diffuse, and fundamental, and later these terms were applied to the secondary quantum numbers.

After fundamental, alphabetical order is used for subsequent letters. In practice, examples in nature rarely get much further up the list.

They are also referred to as sub-shells. But note what I said above about shells.

In theory, the behaviour of electrons can be determined from a function called an atomic orbital. In practice it may only be possible to obtain an approximation. The n and l values are the result of this calculation. Just to make things even more complicated there are two more characteristics that come from this: the magnetic Q.N. which can take integer values from -l to +l; and the spin Q.N. which can only take values of +½ or -½.

It is widely claimed that for a given atom no two electrons may have exactly the same Q.N.s Professor Brian Cox says that no two electrons in the entire universe may have the same energy state as any other! http://physics.stackexchange.com/questi … -electrons In this series of exchanges, no poster actually says he watched the programme, but I did, and I can confirm that he did say this. I think he may be occupying a different universe from the rest of us however as there are many reasons why this cannot be so. As he is widely acknowledged as an expert on this in the UK, it just goes to show the truth of the Feynman quote.

If you're still reading at this point, well done. I got lost several paragraphs ago.

If you're studying this topic and can shed any light ( photons ? ) that will help us make sense of Q. Mechanics then please post away.

Bob

*Last edited by bob bundy (2013-12-05 02:08:40)*

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,917

Hi Bob

I'd say that is the current standard.

In previous physics lessons we learned also that the electron energy levels of an atom in a molecule are split up into sublevels because of the forces in the molecules and the fact that electrons interact with other nuclei as well as their own.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,861

Stefy wrote:

I'd say that is the current standard.

What! Are you saying that what I have written is a correct interpretation of current thinking on the subject?

If so, then I am amazed. I was expecting a flood of corrections.

Bob

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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,044

bob bundy wrote:

I am amazed. I was expecting a flood of corrections.

well,i am just a novice on quantum mechanics and your article on it was as always understandable and satisfactory for me right now.

I wanted to know the basics and i got it.

thank you.

Will surely add more to it when I get to know it more next year.

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**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,640

Nikharika, I may be wrong but I don't think they cover quantum numbers in the CBSE 10th standard curricula. A forum you can try, even though there are several science enthusiasts on here, is physicsforums.com.

Agnishom, I have seen from the syllabus that the ICSE curricula is more rigorous then CBSE. I checked around meritnation for the content and to me it seems quite similar. Optics, basic Classical Mechanics and I think there was some EM.

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,917

Hi Bob

I have only one correction -- h=5*.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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Thanks for explaining.

Shivam: Do you have an idea about where ICSE books can be downloaded from

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,044

Yes shivam its not in class 10.But the question came in NTSE so just wanted to know what it is basically.

by the way in which class are you now?

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,861

Stefy wrote:

I have only one correction -- h=5*.

Thanks. Just a typo; phew. I have changed it.

Bob

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**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,640

Agnishom wrote:

Thanks for explaining.

Shivam: Do you have an idea about where ICSE books can be downloaded from

Unfortunately I couldn't find any downloadable online version of those books. But, I think you can safely assume that they are pretty similar to NCERT. By the end of 12th, you have pretty much covered the same material from CBSE, CISCE and the state boards.

Nikarika, I am in university.

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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,044

oh, i see.

may I know which year and course?

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,917

Also, because I did not see Bob mention it, the magnetic Q.N. describes the direction of angular momentum.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,640

niharika_kumar wrote:

oh, i see.

may I know which year and course?

I took a bit of a weird route but technically am second year biology student.

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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,044

biology student in mathisfunforum?

sounds really weird.

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,917

Why is it weird that people have various interests?

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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