Understanding Shells' Arrangement

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Discussion Overview

The discussion centers around the arrangement of electrons in atomic shells, specifically why the first shell can only accommodate two electrons and the concept of sub-shells. It touches on quantum numbers and their roles in defining electron configurations, with references to quantum mechanics.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Homework-related

Main Points Raised

  • Some participants inquire about the limitation of two electrons in the first shell, referencing the Pauli exclusion principle and the associated quantum numbers.
  • One participant explains that the first shell corresponds to n=1, which allows for only one sub-shell (l=0), thus permitting only two electrons due to the two possible values of the spin quantum number (ms).
  • There is a discussion about the definitions of quantum numbers (n, l, m) and their significance in determining electron configurations and sub-shells.
  • Some participants suggest that understanding quantum mechanics is necessary to grasp the concepts of sub-shells and quantum numbers fully.

Areas of Agreement / Disagreement

Participants generally agree on the basic principles of quantum numbers and their implications for electron arrangement, but there is no consensus on the depth of understanding required or the best resources for learning.

Contextual Notes

Some participants express uncertainty about the definitions and roles of quantum numbers, indicating a need for further clarification and study. There are references to Schrödinger's equations, but the discussion does not resolve the complexities involved in learning quantum mechanics.

Jadaav
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Hi,

Why does the 1st shell only can have 2 electrons in it ?

Also what are sub-shells ?
 
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Jadaav said:
Hi,

Why does the 1st shell only can have 2 electrons in it ?

The Pauli exclusion principle says electrons in atoms cannot share the same 4 quantum numbers. The fact that the electrons are in the 1st shell determines 3 of them (n=1, l=0, ml=0), and there are only two possible values for the 4th quantum number (ms=+1/2 and ms=+1/2). Got it?

Also what are sub-shells ?

Well, for principal quantum numbers higher than n=1, there are multiple possibilities for the value of the angular momentum quantum number l (l=0 up to l=n-1). Each possible value of l is associated with a sub-shell: l=0 is called the s-subshell, l=1 is called the p-subshell, and so on.
 
What is the quantum number ?

and n,I and m ?
 
Jadaav said:
What is the quantum number ?

and n,I and m ?

The quantum number is something you should already know about if you are asking the question in your original post :wink:. Seriously though, please look that up on wikipedia to get the basics down, then come back here and ask specific questions if you are confused.
 
To know that, you need to learn quantum mechanics a little bit. Sub-shells are orbitals, determined by quantum numbers in Schrödinger's equations. n is the principal quantum number that determines the shell. l has something to do with angular momentum, m is the magnetic angular quantum number.

In general, l must be less than n, while m must be equal to or less than l. In the first shell n=1 as it is the first shell, l only =0. In the second shell where n=2, l=0 or 1, so m=+1 or -1 or 0. For each set of parameters there is one orbital and in one orbital there are two electrons. Thus in first shell there is only on orbital possible, thus 2 electrons.

I hope this would help you with your question.
 
ZealScience said:
To know that, you need to learn quantum mechanics a little bit. Sub-shells are orbitals, determined by quantum numbers in Schrödinger's equations. n is the principal quantum number that determines the shell. l has something to do with angular momentum, m is the magnetic angular quantum number.

In general, l must be less than n, while m must be equal to or less than l. In the first shell n=1 as it is the first shell, l only =0. In the second shell where n=2, l=0 or 1, so m=+1 or -1 or 0. For each set of parameters there is one orbital and in one orbital there are two electrons. Thus in first shell there is only on orbital possible, thus 2 electrons.

I hope this would help you with your question.

OK, thanks I'm going to learn quantum mechanics first.
 

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