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# Atomic Spectroscopy-Need help today!!

Submitted by Anonymous (not verified) on Thu, 03/17/2011 - 12:57

I need some help with these problems I am completely stumped can someone walk me through how to do these? I’m not asking for you to do them for me I just want to know how to do them, or where to start.

Wavelength 632 nm , I found the frequency to be 4.75 *10^14 sec , and the energy of a photon of this electromagnetic radiation to be 3.15*10^-19 J. It then asks for the energy of one mole of photons of this radiation? I am completely stuck on how to find that.

2) What is the energy found in the n=4 level of a hydrogen atom? Is the electron in this atom in ground state?
Given: En=-2.1788*10^-18J/n^2
I am used to work with problems that say when it jumps from level such to level such but on this I am stuck. Also the En is confusing me…

3)The electron transitions where an electron falls from a Bohr orbit having a value n>4 to the n=4 orbit gives rise to a series called  Brackett series. Calculate the wavelength of the lowest enegy electromagnetic radiation given off in this series of lines. What is the wavelength of the highest energy line in the Brackette series?
Give: triE=-2.1788*10^-18 J[1n/f^2-1n/i^2]

I am completey stumped on this one.
I spent all night trying to figure these out and scanning through my notes and book but am completely lost. Any help will be highly appreciated! This is due today also so really need some help. Again since it’s an assignment I have to do it I only need some guidance to this not answers.

1)A mole is a collection of 6.02 x 1023 objects (Just like a dozen is a collection of 12 objects).
If they asked you for the energy of a dozen photons, you would take the energy of a single photon and multiply by 12.  If your asked for the energy of a mole of photons, then you take the energy of a single photon and multiply by 6.02 x 1023.

2) The electron is not in the ground state which would be n=1 (the first energy level).  They are telling you how to calculate the Energy value of an electron with the equation:
En=-2.1788*10^-18J/n^2
If you wanted to calculate the energy of an electon in the 2nd energy level (n=2) you would get
E2nd=-2.1788*10^-18J/2^2
For n=4 it would be
E4th=-2.1788*10^-18J/4^2

3) Based on a Wikipedia article, the lowest energy transition in the series is between the 4th and 5th energy levels.  f in the equation stands for final and i stands for initial energy levels.