3 ms·

I’d love to read more. Can you or someone else provide a relevant link?

Synaesthesia 6y ago
Well classically, atoms wouldn’t even be stable. Their electrons would radiate energy when orbiting and therefore spiral into the nucleus. So without quantum physics you don’t have fundamental properties of atoms like energy levels which explains their chemical properties.
- shakow 6y ago
  > Their electrons would radiate energy when orbiting What phenomenon would make them lose energy?
  - jbay808 6y ago
    Under the assumption that the electron is a point charge moving in a circular path, it radiates electromagnetic energy as it moves, in the form of field ripples. This gif is for a 1d oscillation rather than an orbit, but it does a good job of conveying the idea. https://thumbs.gfycat.com/ExhaustedAlarmedDeinonychus-size_restricted.gif https://thumbs.gfycat.com/ExhaustedAlarmedDeinonychus-size_r... Interestingly enough, if the electron were a continuous ring (like Saturn's rings) rather than a point charge, it could orbit without losing energy, generating only a static magnetic field. I don't know why this model rarely comes up in explorations of classical physics models of the atom.
heavenlyblue 6y ago
I remember I once found a website that started by simply explaining that all electron orbitals are quantised because there must be an whole number of waves an electron would make around the orbital or otherwise the wave function would start cancelling itself (and thus this energy has got to go somewhere).
- ridiculous_fish 6y ago
  This sounds a bit like old quantum theory: https://en.wikipedia.org/wiki/Old_quantum_theory https://en.wikipedia.org/wiki/Old_quantum_theory I'd say the intuition here is misleading. S orbitals (including the ground state) really are spherically symmetric. There are no waves "around" the orbital: they only vary in the radial direction. But "must smoothly connect" is important. As you walk outwards from the nucleus, the electron wavefunction oscillates until it reaches the classical turning point, when it switches to exponential decay. Only a very few functions can smoothly join these two modes, which is one explanation for why bound state energies are quantized.
  - heavenlyblue 6y ago
    I think it only depends on how you visualise the wave function. In that case the drawing was 2-dimensional, but the wave function was defined as a third dimension (it was orthogonal to the plane in which the electron was orbiting the nucleus). It was reasonably clear to me that either the size of the wave was incredibly small compared to the size of the orbital or it was oscillating in some other dimension.
ridiculous_fish 6y ago
I'll plug my site, which visualizes solutions to the Schrödinger equation in 1d potentials. Try the first two exercises, no math required: https://ridiculousfish.com/wavefiz/#exercises https://ridiculousfish.com/wavefiz/#exercises
karlicoss 6y ago
Perhaps this, in particular "The hydrogen molecule" section https://www.feynmanlectures.caltech.edu/III_10.html https://www.feynmanlectures.caltech.edu/III_10.html

Well classically, atoms wouldn’t even be stable. Their electrons would radiate energy when orbiting and therefore spiral into the nucleus. So without quantum physics you don’t have fundamental properties of atoms like energy levels which explains their chemical properties.

shakow 6y ago
> Their electrons would radiate energy when orbiting What phenomenon would make them lose energy?
- jbay808 6y ago
  Under the assumption that the electron is a point charge moving in a circular path, it radiates electromagnetic energy as it moves, in the form of field ripples. This gif is for a 1d oscillation rather than an orbit, but it does a good job of conveying the idea. https://thumbs.gfycat.com/ExhaustedAlarmedDeinonychus-size_restricted.gif https://thumbs.gfycat.com/ExhaustedAlarmedDeinonychus-size_r... Interestingly enough, if the electron were a continuous ring (like Saturn's rings) rather than a point charge, it could orbit without losing energy, generating only a static magnetic field. I don't know why this model rarely comes up in explorations of classical physics models of the atom.

heavenlyblue 6y ago

I remember I once found a website that started by simply explaining that all electron orbitals are quantised because there must be an whole number of waves an electron would make around the orbital or otherwise the wave function would start cancelling itself (and thus this energy has got to go somewhere).

ridiculous_fish 6y ago
This sounds a bit like old quantum theory: https://en.wikipedia.org/wiki/Old_quantum_theory https://en.wikipedia.org/wiki/Old_quantum_theory I'd say the intuition here is misleading. S orbitals (including the ground state) really are spherically symmetric. There are no waves "around" the orbital: they only vary in the radial direction. But "must smoothly connect" is important. As you walk outwards from the nucleus, the electron wavefunction oscillates until it reaches the classical turning point, when it switches to exponential decay. Only a very few functions can smoothly join these two modes, which is one explanation for why bound state energies are quantized.
- heavenlyblue 6y ago
  I think it only depends on how you visualise the wave function. In that case the drawing was 2-dimensional, but the wave function was defined as a third dimension (it was orthogonal to the plane in which the electron was orbiting the nucleus). It was reasonably clear to me that either the size of the wave was incredibly small compared to the size of the orbital or it was oscillating in some other dimension.

ridiculous_fish 6y ago

I'll plug my site, which visualizes solutions to the Schrödinger equation in 1d potentials. Try the first two exercises, no math required: https://ridiculousfish.com/wavefiz/#exercises https://ridiculousfish.com/wavefiz/#exercises

karlicoss 6y ago

Perhaps this, in particular "The hydrogen molecule" section https://www.feynmanlectures.caltech.edu/III_10.html https://www.feynmanlectures.caltech.edu/III_10.html