Question about energy needed by electron to change energy levels

[songoku]

TL;DR

This learning material is high - school level

Let say hypothetically there are 2 different energy levels in an atom, n =1 state and n = 2 state and at n = 1 the electron has energy level of 5 eV and at n = 2 the electron has energy level of 8 eV.

What happens to the electron, when at n = 1 there is photon of energy 4 eV falls on it? Will it move to n = 2 state or will it stay at n = 1?

Electron can move from lower energy level to higher energy level when it absorbs energy equal to the difference between the energy levels based on equation: $hf = \Delta E$

If the incident photon has lower energy compared to $\Delta E$, then electron won't move to higher energy level. But what about if the incident photon has higher energy compared to $\Delta E$?

1. Will the electron still move to n = 2 by only absorbing 3 eV from the photon and "ignoring" the remainder 1 eV? If yes, what happens to the remainder 1 eV?

2. Or maybe the electron just stay at n = 1 because the energy of photon does not match the required energy to move to n = 2, even tough the energy is more than required?

Thanks

 

[PeterDonis]

Will it move to n = 2 state or will it stay at n = 1?

It will stay at n = 1.

 

[songoku]

It will stay at n = 1.

So what happens to the photon carrying the 4 eV energy? Will the photon disappear and all the energy is dissipated as heat inside the atom or the photon will just bounce off the electron and moving away carrying all the 4 eV energy or maybe something else?

Thanks

 

[etotheipi]

So what happens to the photon carrying the 4 eV energy?

Remember, that you must conserve momentum and energy of the atom+photon system! This is a scattering process.

 

[songoku]

Remember, that you must conserve momentum and energy of the atom+photon system! This is a scattering processs

Are you maybe referring to Compton scattering? The photon will hit the electron and then move at certain angle to conserve momentum, and some of energy of initial photon will be transferred to electron (as KE of the electron) so the scattered photon will have lower energy compared to initial photon?

This means that the electron will move (because it gains KE) but will not change state?

Thanks

 

[PeterDonis]

So what happens to the photon carrying the 4 eV energy?

It doesn't get absorbed. It might scatter off the atom.

 

[songoku]

Thank you very much PeterDonis and etotheipi