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Chemistry Why does this equation not give me the ionization energy of lithium?

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6
Homework Statement
i want to find the first ionization energy for lithium using Bohr formula but something seems wrong !
Homework Equations
Bohr energy equation
i am trying to calculate the first ionization energy for lithium with this equation but it seems to work only with hydrogen ?
i put nf = infinity and ni =2 ,and z = 3 for lithium and it gives about 30 ev not 5.39172 ev which is the value for lithium :

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i will appreciate any help in this
 

Borek

Mentor
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2,519
There are some limitations to the Bohr model, do you know them?
 
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There are some limitations to the Bohr model, do you know them?
i know that it failed to describe the experimental results for multi electron atoms :smile: ,
so what equation is being used for finding the ionization energy ?
because every where i look online it seems that people uses that equation ?!
 

mjc123

Science Advisor
777
347
Look up "Rydberg atom". Your equation is for a hydrogen-like ion, with 1 electron, i.e. Li2+.
 
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Look up "Rydberg atom". Your equation is for a hydrogen-like ion, with 1 electron, i.e. Li2+.
thanks i got it now , so i am assuming that there is no equation that could calculate the first ionization energy of a specific element except hydrogen ?!
or even approximately at least ?
 

mjc123

Science Advisor
777
347
Not really, without computer number-crunching. Practically, I think it would work the other way round - measure the ionisation energy, calculate the quantum defect, compare periodic trends and see what that tells you about the orbitals.
 

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