Why are the wavelengths of light emitted by an atom unique to that atom ?

Question

Why are the wavelengths of light emitted by an atom unique to that atom ?

Answer 1

Are you talking about when an excited electron jumps levels?

Answer 2

All atoms have discrete energy shells in whjich electrons, depending on their energy, can travel in. If an electron gains a specific amount of energy, it can "jump" to higher levels, but it takes an exact amount of energy to do so, with the amount being dependant on it's mass.

Thus the energy required for an electron to "jump" to another level would be less for an oxygen atom than it would be for a thorium atom, for example.

These jumps are only temporary, as it is an unstable state for the electron to be in.

Thus when the electron returns to it's normal shell, it either gives off a photon equal to the energy that was absorbed to bring the electron to an excited state, or if it jumped several levels, it can "cascade" back down to it's normal shell and give off photons of several different wavelengths depending on how many levels it cascades down.

I hope this answers your question?

Answer 3

Since you're specifically asking about emitted light, which is caused by excited electrons collapsing to lower energy levels, it may be easier to think of this through an analogy. The sound a bowling ball makes when it is dropped from 1 inch above the floor is different than the sound it makes when it is dropped from 10 feet.

Answer 4

Because each element (atom) has a unique nuclear charge. (Atomic number)

The nuclear charge is responsible for the energy eigenstates of the electrons about the nucleus, and thus the wavelengths of light emitted by the atom.