How can two atomic orbitals with the same n value be orthogonal?

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Discussion Overview

The discussion revolves around the orthogonality of atomic orbitals, specifically focusing on how orbitals with the same principal quantum number (n), such as 2s and 3s, can be orthogonal. Participants explore the implications of orthogonality in quantum mechanics and the significance of radial nodes in wave functions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants express confusion about how 2s and 3s orbitals can be orthogonal despite the 3s being larger than the 2s orbital.
  • It is noted that the property of orthogonality requires the integral of the product of two wave functions to equal zero over all space.
  • One participant mentions that 2s has one radial node and 3s has two, suggesting that the change in sign of the wave functions around these nodes contributes to their orthogonality.
  • A later reply introduces the idea that the integral of the products of wave functions, such as 1s x 3s and 2s x 3s, can also integrate to zero, despite the orbitals not being equal to each other.
  • Another participant suggests looking into Linear Algebra and Differential Equations to understand the orthogonality of wave functions as solutions to the Schrödinger Equation.
  • There is a comparison made between the orthogonality of wave functions and the orthogonality of unit vectors in 3D space.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the understanding of orthogonality in orbitals, and multiple competing views remain regarding the implications and explanations of the phenomenon.

Contextual Notes

There are limitations in understanding due to the complexity of wave functions and the mathematical treatment of orthogonality, including the dependence on the definitions of radial nodes and the nature of the integrals involved.

fsci
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I am wondering how two orbitals of same n values can be orthogonal, for example how are a 2s and 3s orbital orthogonal?
What I understand is a property of orthogonality is the product of the two wave functions integrate to zero over all space. I tried to look at this graphically and categorize overlapping regions as either positive or negative products and then cancel out positive and negative regions to yield zero, but what I am having trouble is that the 3s orbital is larger than the 2s orbital, so how can they possible integrate to zero?
If someone could also explain the significance/implications of all orbitals being orthogonal that would be helpful too! I do not understand the importance of orthogonality in orbitals!
Thank you!
 
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fsci said:
I am wondering how two orbitals of same n values can be orthogonal, for example how are a 2s and 3s orbital orthogonal?
What I understand is a property of orthogonality is the product of the two wave functions integrate to zero over all space. I tried to look at this graphically and categorize overlapping regions as either positive or negative products and then cancel out positive and negative regions to yield zero, but what I am having trouble is that the 3s orbital is larger than the 2s orbital, so how can they possible integrate to zero?
If someone could also explain the significance/implications of all orbitals being orthogonal that would be helpful too! I do not understand the importance of orthogonality in orbitals!
Thank you!

There are radial nodes that you usually cannot see in the higher n (n>=2) representations, as typically drawn. 2s has one radial node, 3s has two radial nodes. On either side of the radial node there is a change in sign for the wave function.

When you do the integral for any of the products you will get positive regions cancelling the negative regions.
 
Quantum Defect said:
There are radial nodes that you usually cannot see in the higher n (n>=2) representations, as typically drawn. 2s has one radial node, 3s has two radial nodes. On either side of the radial node there is a change in sign for the wave function.

When you do the integral for any of the products you will get positive regions cancelling the negative regions.

Ok thank you. I may be heading in the wrong direction... But how do the product of a 1s x 3s and then product of a 2s x 3s both integrate to zero when 1s and 2s orbitals are not equal to each other?
 
fsci said:
Ok thank you. I may be heading in the wrong direction... But how do the product of a 1s x 3s and then product of a 2s x 3s both integrate to zero when 1s and 2s orbitals are not equal to each other?

You might look into some Linear Algebra, Differential Equations textbooks. For the H-atom wave functions, you will have an infinite set of wavefunctions, that are solutions to the Schroedinger Eq. Each l=0 wavefunction will be "orthogonal" to the other, as long as n_1<> n_2.

This is kind of like the way that the unit vectors in 3D space are all orthogonal to one another. x_hat dot y_hat = 0, x_hat dot z_hat = 0, y_hat dot z_hat =0.

The solutions to the Schoredinger Eq for H are like these basis vectors in 3D space, except the space is infinite.
 

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