Why can electrons only be at certain levels?

Question

If an electron is orbiting an atom, it can only exist in certain shells. Why can't an electron orbit an atom at any energy level, just like a moon could orbit a planet at pretty much any altitude? I welcome both short and long answers. I would especially appreciate links to diagrams or web sites that explain this well.

Answer 1

The orbitals are not simple. The main constraint you are talking about is the quantum constraint. This is the scale on which quantum effects become significant. Because of the wave nature of the electron, the length of its orbit must be an integral multiple of the wavelength of its wavefunction. From its base (lowest energy) orbit, an outer shell electron can absorb a photon and move to a higher orbit. From there, it can emit a photon and drop back to its base orbit. Electrons can inhabit shells and subshells only singly or in pairs of opposite spin. Sometimes the next electron will populate a new shell rather than fill our a lower shell or subshell. If you want to understand it, you'll need a book on physical chemistry.

Answer 2

The reason why the electron can only orbit certain shells is that stable orbits are quantized. The key here is that everything on a microscopic level is quantized. This is just a short general answer. There are a lot of other details involved but they all point to quantum mechanics and quantization of energy.

The moon cannot orbit a planet at pretty much any altitude either. If it is too far and not fast enough it will drift away. If it is too slow and close it will spiral into the earth. If it is too close and fast enough to be in orbit it might be within the roche limit and break apart to form a ring a debris like the rings of Saturn and Jupiter and the other Jovian planets. This is some other type of physics though, not really related to quantization.

Answer 3

The sunlight isn't white yet a yellowish colour. the colour of the sunlight tells us what frequency of sunshine is being emmitted , we can seem on the emmision spectra of sunlight hours and notice bands which correspond with the capability tiers of electrons in hyrogen , and helium. e=hf capability = planks consistent x frequecy of emmitted easy frequency = colour seen yet might nicely be a mix of countless guy or woman frequencies.

Answer 4

It's because of Pauli's Exclusion principle.