Lesson 4.1 Energy

Level Diagrams Here is a model of an atom n=1 n=0 (ground state) n=2 n=3 an electron originating in the ground state can jump to another energy level assuming it has the correct energy (just like a leprachaun trapped in a well) n=0 n=3 n=2 n= n=1 (Free electrons) -13.6eV -3.4eV -1.5eV -0.85eV 0eV 10.2eV 12.5eV 12.75eV 13.6eV 8 The energy required to jump between levels can be determined by working out the difference in energies between levels 1.9eV 2.55eV 3.4eV 0.65eV 1.5eV 0.85eV These energies correspond to the absorption lines seen in spectra So knowing the missing frequencies/wavelengths allows us to determine the energy levels in atoms E= hf= hc \ / | where h is Planck's constant and is 6.63 x 10 -34 n=0 n=3 n=2 n= n=1 (Free electrons) -13.6eV -3.4eV -1.5eV -0.85eV 0eV 10.2eV 12.5eV 12.75eV 13.6eV 8 1.9eV 2.55eV 3.4eV 0.65eV 1.5eV 0.85eV Example 1 What is the frequency of light required to move an electron from the ground state to n=2? Step 1 - determine the change in energy required (from diagram)

Step 2 - convert this energy into joules

*note that the energy in this case is measured in Joules and not eV, 1eV=1.6 x 10 Joules -19 Step 3 - Use the equation E=hf to determine the frequency of light necessary 12.5 eV (12.5 eV) x (1.6 x 10 J) = 20 x 10 J -19 -19 20 x 10 J = (6.63 x 10 ) x f -19 -34 f=3.02 x 10 Hz 15 But what happens to these electrons once they jump to an 'excited state'? Simple! they jump back down When this happens, instead of absorbing a photon of energy, they emit it which explains how we can get emission spectra.

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# Quantum Physics Lesson 4.1 - Energy Level Diagrams

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