The emission lines we see in a spectrum are due to

This preview shows page 2 - 3 out of 3 pages.

The emission lines we see in a spectrum are due to changes in energy levels (stationary states). We can compute these wavelengths from Bohr's result for the energy levels of an electron in an atom E i = - 1 2 Z 2 E 2 a o n i 2 and the spectral line is given by E = E i - E f
Image of page 2

Subscribe to view the full document.

E = 1 2 Z 2 e 2 a o ( 1 n f 2 - 1 n i 2 ) where 1 2 Z 2 e 2 a o R z or R z = Z 2 R And R is known as the Rydberg constant and is calculated with Z = 1 (hydrogen atom) R = 1 2 e 2 a o = 1 2 (1.60 x 10 -19 C) 2 (0.530 x 10 -10 m) x (9 x 10 9 J m) c 2 R = 2.18 x 10 -18 J or by using energy conversion factors: R = 109678 cm -1 = 13.60 eV = 313.6 kcal mole -1 There is one more detail - we have been working with the assumption that we know n i & n f and want to obtain E or λ - we could also perform an experiment that measures λ . Using Planck's law E = hc λ we could obtain E ( and n i , if n f is already known). All of the quantum theory we have done is applicable. You must be able to work in all possible directions using these expressions.
Image of page 3
You've reached the end of this preview.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern