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Physics/Energy and Bohr's model


QUESTION: According to Bohr's model, the third orbit of a hydrogen atom would have an energy of (-1.15ev) , in some other textbooks I've seen  the value written as (13.6-1.15) , where 13.6 is the energy of the the first orbit.
Which one is correct? And if I were asked to state the energy of an electron in that level would it be the 1.15 or 12.45 in this case?
Note: all energies are in electro volts

ANSWER: The energy levels in the hydrogen atom are given by:
U=-13.6/n^2 eV
For the first four levels:
n=1  U=-13.6eV
n=2  U=-1.51eV
n=3  U=-.85eV
n=4  U=-.54eV
I do not know where you are getting your numbers from.

---------- FOLLOW-UP ----------

QUESTION: Sorry I meant second level , and the 12.45 is the result of finding the difference between the second and first orbits' energies . You haven't answered my question yet sir...
Is 12.45 the energy of the ELECTRON in the SECOND orbit ? Or is -1.51 the ELECTRON's as well as the ORBIT's energy?

All these numbers tell you is how much energy you must supply an electron in a particular orbit in order to remove that electron from the atom. For example an electron in the lowest energy level of hydrogen will require an input of 13.6eV in order to remove that electron from the atom. In that sense an electron in the lowest energy level has -13.6 eV of energy and needs at least 0.0eV of energy to escape. An electron in the n=2 orbit, by comparison will only require the addition of 1.51eV of energy to liberate that electron from the atom.


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James J. Kovalcin


I am teaching or have taught AP physics B and C [calculus based mechanics & electricity and magnetism] as well as Lab Physics for college bound students. I have a BS in Physics from the University of Pittsburgh and a Master of Arts in Teaching from same. I have been teaching physics for 34 years. I am constantly updating my skills and have a particular interest in modern physics topics.

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