## Practice problem

H-Atom ($E_{n}=-\frac{hR}{n^{2}}$)

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904901860
Posts: 24
Joined: Mon Jan 08, 2018 8:16 am

### Practice problem

I’m not sure how to go about this problem, I know the answer is n=5 but I’m still struggling on how to get there.

In a hydrogen atom, an electron transitions to the second quantum level from another quantum level and caused a photon with a frequency of 6.91 x 10^14 Hz to be emitted. What was the initial energy level?

Thank you in advance if you help!

Ashish Verma 2I
Posts: 59
Joined: Fri Sep 28, 2018 12:28 am

### Re: Practice problem

The question focuses on using this quantum equation for hydrogen: $E_{n}=\frac{hR_{h}}{n^2}$
Manipulating the equation with the information given, (the energy released as the electron went from one energy level to another) you get:
$E=\frac{hR_{h}}{n_{f}^2}-\frac{hR_{h}}{n_{i}^2}$
Where:
E = The energy released during the quantum transition (solve using $E=h\nu$ as you are given frequency)
h = Planck's constant, $6.62608*10^-34 J*s$
$R_{h}$= Ryderg constant, $3.28984*10^15Hz$
$n_{f}$= the final quantum level of the electron, given to be n = 2
$n_{i}$= the initial quantum level of the electron, (what you're solving for)

Plug in all of that correctly and you should get n = 5!

904901860
Posts: 24
Joined: Mon Jan 08, 2018 8:16 am

### Re: Practice problem

Thank you!

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