Spectra and Atoms continued:

One of Nature's most basic rules:

Systems naturally seek their lowest available energy state - or - logs roll downhill

• So, left alone, hydrogen atoms tend to be in the ground state.

Now, let's bombard an H atom with photons. What happens? Most of the photons go zipping right past without interacting with the H atom. But! photons with just the RIGHT energy get absorbed by the atom

Right means that the energy of the photon corresponds to the energy level difference between ``allowed'' orbits in the H atom. Absorbed means that the energy of the photon will now be gone and the atom will be in a higher energy state.

• A photon with frequency will be absorbed by an atom if the energy of the photon corresponds to an energy level difference between allowed states in the atom

• What happens next? Remember, Nature seeks the lowest available energy level so the bumped to an excited orbit will drop back to the ground state.

• Another Law of Nature, Conservation of Energy , states that the energy difference between the excited state and ground state must appear somewhere when the atom makes the transition. ``Somewhere'' is as a photon with the energy of the original one.

  

• Below is a schematic diagram of the allowed orbits in a Hydrogen atom. If you can answer the questions about it, you've got the idea.

  

  1. Which transition(s) correspond(s) to the absorption of a photon?

  2. Which transition corresponds to the highest energy photon emitted ?

  3. Which transition corresponds to the shortest wavelength photon emitted?

  4. Which transition corresponds to the higest frequency photon emitted?