Ionization Energy: Hydrogen

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What is the ionization energy for H if its electron is in ground state?

The easiest way to solve this problem is by using the Rydberg expression:


1lambda=R(1n121n22)\frac{1}{lambda}=R\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right)

lamda=wavelength in m
R=is the Rydberg constant (1.097 x 107/m)
n1=principle quantum # of the lower energy level
n2=principle quantum # of the higher energy level

For Hydrogen, how many electrons does it have?
1
Where would the electron that we are removing be found if we were told it is in ground state? n=
1
This tells us that n1=1
What should n2 be then?

Rearrange and solve for lamda:




Now that we have the wavelength, how do we find energy? Write out the equations that we know:


E=hv and c=lamda(v)

This means we can use our knowledge of the wavelength and speed of light (3.0x108 m/s) to solve for frequency first, then when we know the frequency we can solve for E since h is just a constant (6.63x10-24)

Using c=lamda(v) solve for frequency:



Using E=hv solve for Energy:




More How Atomic Spectra Relates to Electronic Transitions + Other Applications of the Bohr Model Questions: