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### Hydrogen Atom / Quantum Level

Posted: Sun Oct 11, 2015 7:31 pm
"An excited hydrogen atom emits light with the frequency of 1.14 x 10^14 Hz to reach the energy level for which n=4. In what principal quantum level did the electron begin?"

How do I go about solving this problem? I am kind of confused on which equation(s) to use.

### Re: Hydrogen Atom / Quantum Level

Posted: Sun Oct 11, 2015 10:23 pm
You can use the equation $En=\frac{-hR}{n^{2}}$.

Change in energy for the electron "$\Delta E$" = E4-En. In other words, energy of electron at n=4 minus energy of electron at initial state n.

So, solve the equation for En, which represents the energy of the electron at its initial quantum level n.

You can rewrite the term "$\Delta E$" as hv. Then, you plug in 1.14x1014 Hz as your frequency v. From there you should be able to solve for "n".

More information can be found on pages 6-8 of the textbook.

Good luck! :)