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I am confused about spectral analysis. I understand that when electrons rise/fall into another orbital they absorb/emit photons of equivalent energy to their change from/ back towards ground state. Where im confused is why dose the amount of energy for this change of an elements electrons orbits vary from element to element, resulting in different wavelengths of light being absorbed/emitted. So for example lets take two noble gasses, neon and argon and add enough energy to expand the electron shell out one space so neon's 8 electrons go up to the 3rd shell and with argon 8 electrons go the same "distance"(not sure if this is the proper nomenclature) to the 4th shell. So in both cases you have the same number of electrons moving the same "distance" so I'd think the requisite energy would be the same and so absorb the same wavelengths of light resulting in the same spectral analysis patter, but this isn't what happens so I'm just wondering what am I missing?

Nathan Bladow
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2 Answers2

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The problem is the energy difference between the 4th and 3rd energy shells is not the same as the energy difference between the 3rd and 2nd energy shells. The reason they are referred to as the 1st, 2nd, or 3rd energy shell is not because they are somehow the same 'distance' from each other, but because the 1st shell is more tightly bound than the 2nd shell which is more tightly bound than the 3rd shell. The actual energies depend on how the quantum mechanics work out.

Additionally, while you can solve for the exact energy levels when you only have a single electron(for example, in hydrogen) as soon as you add a second electron, the charges start to interact and change the orbital energies in complex ways. So even if you're looking at the 20th electron in one atom versus the 20th electron in another atom, the energy levels won't necessarily be the same. Each atom will have it's own corrections.

MonkeysUncle
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MonkeysUncle covers the main problem, but consider another effect: the atoms have different numbers of protons. Suppose we stripped it down to hydrogen vs. ionized helium. One of them has one electron and one proton, and one of them has one electron and two protons. For helium, you can therefore imagine that the electron is more tightly bound, so it will be harder for the electron to "climb out" to the next orbital.

zeldredge
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