ENERGY LEVEL DIAGRAMS
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Below is a way to picture a hydrogen atom
The electron will be in the ground state
Energy can be put in to the atom
This will excite the electron
The electron will emit a photon and return to the ground state
For Example:
 Say an electron is in the ground state
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If you put in exactly 10.2eV of energy, it will be excited to the n = 2 excited state
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This electron wants to return to the ground state
It will do so by emitting a photon of 10.2eV
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Once you know the Energy of the photon, you should be able to calculate the
frequency and/or the wavelength
E = hf
E = hc / 
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The energies are typically negative values
This is because zero is at the “top”
Every element can have an electron removed, so that is made zero
Each element has a different depth of a ground state
For example:
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It’s making zero PE at the top instead of at the bottom
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If the electron were excited to the n = 3 energy level, 12.09eV needs to go in
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There are three possible photons that can be emitted
A single 12.09 eV photon
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And two more, one that is 1.89eV and another 10.2eV
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Remember, all energy values need to be in Joules when you are going to use an
equation that involves h (Planck’s constant)
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You reminder is the units for Planck’s constant are Joules times seconds
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The conversion is on the front of the reference tables
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If you are not good at conversions:
o Muliply eV by 1.6x10-19J/eV to get Joules
o Divide Joules by 1.6x10-19J/eV to get electronvolts