Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: aFarDay on November 09, 2010, 07:59:17 PM

Title: How do I calculate the Rydberg Constant?
Post by: aFarDay on November 09, 2010, 07:59:17 PM

I was just curious as to how Rydberg came to the conclusion that the Rydberg Constant was approximately  2.18x10^(-18) Joules.

I know The equation is
 R_H = me⁴ / 8E₀²h²
where  h is plancks constant,  E₀ is permitivity constant, M is electron mass, and e is electron charge.

If i put these #'s in will i get 2.18x10^(-18) J?
__________________

Also why is the Rydberg Constant on wikipedia different from the one in my textbook? (zumdahl)



Will Dividing the Rydberg constant by the principal quantum number times -1. Will that give  me En ,the binding energy?

________________

thank you for your help, we are on this chapter but my teacher isn't going in depth with this specific topic in the class.  :)

Title: Re: How do I calculate the Rydberg Constant?
Post by: Borek on November 10, 2010, 04:29:33 AM

Quote from: aFarDay on November 09, 2010, 07:59:17 PM

If i put these #'s in will i get 2.18x10^(-18) J?

Have you tried? 1 minute of keying the digits into the calculator and you will know.

Quote from: aFarDay on November 09, 2010, 07:59:17 PM

Also why is the Rydberg Constant on wikipedia different from the one in my textbook? (zumdahl)

Do they use the same units?

Title: Re: How do I calculate the Rydberg Constant?
Post by: aFarDay on November 10, 2010, 10:49:37 AM

Quote from: Borek on November 10, 2010, 04:29:33 AM

Quote from: aFarDay on November 09, 2010, 07:59:17 PM

If i put these #'s in will i get 2.18x10^(-18) J?

Have you tried? 1 minute of keying the digits into the calculator and you will know.

Quote from: aFarDay on November 09, 2010, 07:59:17 PM

Also why is the Rydberg Constant on wikipedia different from the one in my textbook? (zumdahl)

Do they use the same units?

I have tried and I didn't get anything close to it. I'm sure that there are a lot of different values for those constants in various units. So i don't know which values to plug in.

yeah the value on wikipedia has you multiply the speed of light and another Planck's constant on the denominator.

My calculator gives me either 0 or an error because the #'s are too small and it rounds after about x10^-60

Title: Re: How do I calculate the Rydberg Constant?
Post by: Jorriss on November 10, 2010, 11:04:51 AM

What values are you using for all those inputs?

Title: Re: How do I calculate the Rydberg Constant?
Post by: Borek on November 10, 2010, 11:14:24 AM

Quote from: aFarDay on November 10, 2010, 10:49:37 AM

My calculator gives me either 0 or an error because the #'s are too small and it rounds after about x10^-60

Windows calculator is capable of much higher accuracy (that's assuming you are on Windows). But there is a trick you can use - think if you can change oder of calculations so that your intermediates never get outside of the applicable range.