Atomic & Nuclear Physics AP Physics B
Life and Atoms Every time you breathe you are taking in atoms. Oxygen atoms to be exact. These atoms react with the blood and are carried to every cell in your body for various reactions you need to survive. Likewise, every time you breathe out carbon dioxide atoms are released. The cycle here is interesting. TAKING SOMETHING IN. ALLOWING SOMETHING OUT!
The Atom As you probably already know an atom is the building block of all matter. It has a nucleus with protons and neutrons and an electron cloud outside of the nucleus where electrons are orbiting and MOVING. Depending on the ELEMENT, the amount of electrons differs as well as the amounts of orbits surrounding the atom.
When the atom gets excited or NOT To help visualize the atom think of it like a ladder. The bottom of the ladder is called GROUND STATE where all electrons would like to exist. If energy is ABSORBED it moves to a new rung on the ladder or ENERGY LEVEL called an EXCITED STATE . This state is AWAY from the nucleus. As energy is RELEASED the electron can relax by moving to a new energy level or rung down the ladder.
Energy Levels Yet something interesting happens as the electron travels from energy level to energy level. If an electron is EXCITED , that means energy is ABSORBED and therefore a PHOTON is absorbed. If an electron is DE-EXCITED , that means energy is RELEASED and therefore a photon is released. We call these leaps from energy level to energy level QUANTUM LEAPS. Since a PHOTON is emitted that means that it MUST have a certain wavelength.
Energy of the Photon We can calculate the ENERGY of the released or absorbed photon provided we know the initial and final state of the electron that jumps energy levels.
Energy Level Diagrams To represent these transitions we can construct an ENERGY LEVEL DIAGRAM Note: It is very important to understanding that these transitions DO NOT have to occur as a single jump! It might make TWO JUMPS to get back to ground state. If that is the case, TWO photons will be emitted, each with a different wavelength and energy.
Example An electron releases energy as it moves back to its ground state position. As a result, photons are emitted. Calculate the POSSIBLE wavelengths of the emitted photons.