# Why does exchange occur between electrons having same spin in “degenerate orbitals”?

I am a high schooler and I read in my chemistry book that half filled degenerate orbitals are stable because electrons with the same spin in those degenerate orbitals exchange their positions and this leads to release in some energy.

But one thing which I didn't understand is why do those electrons exchange their position if their respective orbitals had same initial energy.

And also why (and how) does this exchange release energy and cause stability ?

• Could you provide a source for this? – Jakob Feb 6 at 12:45
• Don't take the word exchange that literally. – user137289 Feb 6 at 13:07
• @Pieter then how should I take it ;)? – A Student 4ever Feb 6 at 13:11
• @Astudent I am not a theorist. But in for example an atom with five electrons in the $d$ orbitals, the symmetry of the wave function (when exchanging labels) makes that the electrons are automatically furthest apart when their spins are parallel. This gives then the smallest electrostatic repulsion between them. It is basically due to the Coulomb interaction. – user137289 Feb 6 at 13:45
• @Pieter That should be an answer, but for five electrons occupying 5 different orbitals the spins are not restricted by Coulomb matrix element. It is the direct exchange matrix element that favors parallel spins. – my2cts Feb 6 at 14:44