Atomic Orbitals | n=2, l=1, P Orbital, Magnetic Quantum No.

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Discussion Overview

The discussion revolves around the properties and representations of p orbitals in quantum mechanics, specifically focusing on the magnetic quantum number (m) values associated with the n=2, l=1 state. Participants explore the relationships between the p orbitals (2Px, 2Py, 2Pz) and their corresponding m values, as well as the conventions used by chemists and physicists in labeling these orbitals.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that for n=2 and l=1, the p orbitals correspond to m values of -1, 0, and 1, with specific assignments to 2Px, 2Py, and 2Pz, although there is uncertainty about whether 2Px can be represented by m=0 or 1.
  • Others suggest that the p orbitals may correspond to linear combinations of spatial functions that are eigenfunctions of the Lz operator, indicating a more complex relationship between the orbitals and their m values.
  • It is noted that the direction of the z axis is arbitrary, and m=1 could be assigned to any of the Px, Py, or Pz orbitals, provided the other assignments remain consistent.
  • Some participants highlight a difference in conventions between chemists and physicists regarding the description of orbitals, with chemists using a straightforward x, y, z designation and physicists employing combinations of these orbitals.
  • A later reply indicates that m=+1 and m=-1 states are linear combinations of the Px and Py states, suggesting a more nuanced understanding of the relationships between these orbitals.

Areas of Agreement / Disagreement

Participants express differing views on the correspondence between m values and specific p orbitals, with no consensus reached on the exact assignments or conventions used. The discussion remains unresolved regarding the implications of these assignments and the conventions in different fields.

Contextual Notes

Participants mention the potential confusion arising from the arbitrary nature of the z axis and the implications for the labeling of orbitals. There is also a recognition of the differences in conventions used by chemists and physicists, which may affect interpretations.

Who May Find This Useful

This discussion may be of interest to students and professionals in chemistry and physics, particularly those exploring quantum mechanics and atomic structure.

mkbh_10
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for n=2 & l=1 we have P orbital for which magnetic quantum no. can take values -1,0,1 , now in p orbital we have 2Px, 2Py &2Pz each corresponding to vale of m like 2Px for m=-1 and so on , is this correct or 2Px can be represented by 0 0r 1 also .
 
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According to some general situations in quantum mechanics I would say (not so sure about) that Px (Py and Pz as well) is likely to correspond to some linear combination of the spatial functions which are eigen functions of the Lz operator (m values are eigen values of this operator).

Best wishes

DaTario
 
mkbh_10 said:
for n=2 & l=1 we have P orbital for which magnetic quantum no. can take values -1,0,1 , now in p orbital we have 2Px, 2Py &2Pz each corresponding to vale of m like 2Px for m=-1 and so on , is this correct or 2Px can be represented by 0 0r 1 also .

From http://www.3rd1000.com/chem301/chem301b.htm :


Orbitals with subshell quantum number l = 1 are called p orbitals. Since the magnetic quantum number m can be -1, 0, or +1 when the value of the subshell quantum number l is one, p orbitals come in sets of three. In each set, one of the orbitals is aligned along each of the three mutually perpendicular axes of the atom; these axes are traditionally designated x, y, and z. The three 2p orbitals are correspondingly designated 2px, 2py, and 2pz
 
cadnr said:
From http://www.3rd1000.com/chem301/chem301b.htm :


Orbitals with subshell quantum number l = 1 are called p orbitals. Since the magnetic quantum number m can be -1, 0, or +1 when the value of the subshell quantum number l is one, p orbitals come in sets of three. In each set, one of the orbitals is aligned along each of the three mutually perpendicular axes of the atom; these axes are traditionally designated x, y, and z. The three 2p orbitals are correspondingly designated 2px, 2py, and 2pz

But how nature chooses the particular y and x direction given that magnetic field , for instance, is directed along z axis?

Another correlated comment: I think that your statement does not give an answer to what was asked. If I understood it well the question was: Is it correct to stabilish the correspondence between m=1 and px, m= 0 and py, and m= -1 and pz (or any other bijection) ?

Best wishes

DaTario
 
Last edited:
The direction of the z axis is arbitrary. m = 1 may be assigned to any of Px, Py or Pz. The other two assignments must of course be consistent (orthogonal) with the first. In the labeling of the P prbitals, x, y and z are not related to the initially defined z axis (which may be the cause of some confusion).
 
Perhaps
 
Last edited:
It's standard to take the z axis as arbitrary unless it is specifically defined. And, peculiar as it sounds, you can call the eigenstates anything you want. There is, however a problem: we would be uncomfortable with M |0> = 1|0>, but as a defining equation it's fine -- could have eigenvalue of -1 for state 1, and 0 for state -1. The normal conventions work quite nicely. Good question.
Regards,
Reilly Atkinson
 
could you be a little more detailed?

Thank you in advance,

best wishes

DaTario
 
I think there's a slightly different convention among chemists and physicists for describing the orbitals.

The chemists take three mutually perpendicular orbitals along the x, y, and z axes. Physicists take the z orbital, and then mix the chemists' x and y orbitals into combinations which are basicaly x + iy and x - iy. Now they have three states that are symetrical about the z axis and whose spin is +1, 0, and -1.

A similar thing is done in the d orbitals. The pictures in the chemistry books show orbitals with lobes at 45 degrees, others at 90 degrees, and one with a donut and two lobes. The last one is the one shared with physicists, symetrical about the z axis. The physicists then take mixtures of the chemist's orbitals to get: a pair with spin +/-2, and a pair with spin +/-1 AND a nodal surface through the xy plane (the "equator").
 
  • #10
monish said:
I think there's a slightly different convention among chemists and physicists for describing the orbitals.

The chemists take three mutually perpendicular orbitals along the x, y, and z axes. Physicists take the z orbital, and then mix the chemists' x and y orbitals into combinations which are basicaly x + iy and x - iy. Now they have three states that are symetrical about the z axis and whose spin is +1, 0, and -1.

A similar thing is done in the d orbitals. The pictures in the chemistry books show orbitals with lobes at 45 degrees, others at 90 degrees, and one with a donut and two lobes. The last one is the one shared with physicists, symetrical about the z axis. The physicists then take mixtures of the chemist's orbitals to get: a pair with spin +/-2, and a pair with spin +/-1 AND a nodal surface through the xy plane (the "equator").

Very interesting. But, then, according to what you said, the answer to the question is that m = 1 does not correspond to what we call Px (or Py).

Is it Ok?

Best wishes

DaTario
 
  • #11
DaTario said:
Very interesting. But, then, according to what you said, the answer to the question is that m = 1 does not correspond to what we call Px (or Py).

Yes. The m = +1 and m = -1 states are linear combinations of the Px and Py states; and the Px and Py states are linear combinations of the m = +1 and m = -1 states.
 
  • #12
I feel satisfaction due to this learning moment. Thank you.

Sincerely

DaTario
 
  • #13
DaTario said:
I feel satisfaction due to this learning moment. Thank you.

Sincerely

DaTario

Thanks. I am not used to having people understand my explanations of things.

marty
 

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