# Question about energy needed by electron to change energy levels

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• songoku
In summary, the electron will move to a higher energy level if the incident photon has higher energy compared to the difference between the energy levels, but will not move to a higher energy level if the incident photon has lower energy compared to the difference between the energy levels.
songoku
TL;DR Summary
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

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

It will stay at n = 1.

Wanda and songoku
PeterDonis said:
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

songoku said:
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.

Last edited by a moderator:
songoku and vanhees71
etotheipi said:
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

vanhees71
songoku said:
So what happens to the photon carrying the 4 eV energy?

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

songoku and vanhees71
Thank you very much PeterDonis and etotheipi

## 1. What is the energy needed by an electron to change energy levels?

The energy needed by an electron to change energy levels is known as the energy difference between the two levels. This energy difference can vary depending on the specific atom or molecule, and can be calculated using the Rydberg formula.

## 2. How is the energy needed by an electron to change energy levels related to light emission?

When an electron changes energy levels, it either absorbs or emits energy in the form of photons of light. The energy of the emitted or absorbed light is directly related to the energy difference between the two levels.

## 3. Can an electron change energy levels without absorbing or emitting energy?

No, an electron cannot change energy levels without absorbing or emitting energy. This is because the energy levels of electrons in atoms are quantized, meaning they can only exist at specific energy levels and must gain or lose energy to change levels.

## 4. How does temperature affect the energy needed by an electron to change energy levels?

At higher temperatures, atoms and molecules have more thermal energy, which can cause electrons to jump to higher energy levels. However, this does not change the energy difference between levels, as the energy levels themselves remain the same.

## 5. Can the energy needed by an electron to change energy levels be manipulated?

Yes, the energy levels of electrons can be manipulated through various methods, such as applying an external electric or magnetic field. This can change the energy difference between levels and affect the behavior of electrons in atoms and molecules.

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