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

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SUMMARY

Two atomic orbitals with the same principal quantum number (n), such as 2s and 3s, can be orthogonal due to the presence of radial nodes in their wave functions. The 2s orbital contains one radial node, while the 3s orbital has two, leading to a change in sign of the wave function on either side of these nodes. When integrating the product of their wave functions over all space, positive and negative regions cancel each other out, resulting in an integral of zero. The orthogonality of orbitals is crucial as it allows for the unique representation of quantum states in systems like the hydrogen atom, analogous to orthogonal unit vectors in three-dimensional space.

PREREQUISITES
  • Understanding of quantum mechanics, specifically wave functions and their properties.
  • Familiarity with the Schrödinger equation and its solutions for hydrogen-like atoms.
  • Knowledge of radial nodes and their significance in atomic orbitals.
  • Basic concepts of linear algebra, particularly orthogonality in vector spaces.
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  • Study the solutions to the Schrödinger equation for hydrogen-like atoms.
  • Learn about the significance of radial nodes in atomic orbitals.
  • Explore linear algebra concepts related to orthogonality and vector spaces.
  • Investigate the implications of orthogonality in quantum mechanics and its applications.
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Students and professionals in physics, particularly those focusing on quantum mechanics, atomic structure, and wave function analysis. This discussion is beneficial for anyone seeking to deepen their understanding of atomic orbitals and their mathematical properties.

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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