## Rydberg constant

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

Tiffany Wu 1K
Posts: 19
Joined: Wed Sep 21, 2016 2:56 pm

### Rydberg constant

On the equation sheet, the Rydberg constant is equal to 3.28984*10^15, but on the fall 2014 quiz 1 preparation, the answer for question 10 said otherwise. It uses an equation where R is equal to -2.178*10^-18. Why are there two values for this constant and which one am I supposed to use?

404757006
Posts: 20
Joined: Wed Sep 21, 2016 3:00 pm

### Re: Rydberg constant

The constant he uses in the course reader and the constant and equation sheet he gave us is the 3.289x10^15/3.29x10^15. I'm not sure why the other equation was used for the specific question...

Chem_Mod
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### Re: Rydberg constant

The equation is the same, but one constant is the Rydberg constant by itself which is then multiplied by h, Planck's Constant, in the Rydberg Equation whereas the other is already multiplied by h.

$R=3.29 \times 10^{15} s^{-1}$

$R_h=R\times h = (3.29\times 10^{15} s^{-1})(6.626 \times 10^{-34} J\times s)=2.18\times 10^{-18} J$

Note that the constants are sometimes distinguished by the subscript. Either way, they're both used the same way. When in doubt, take a look at the units and try to figure out where the units differ and why.