The Particle Model of Light and Atomic Emission and Absorption

The Particle Model Under this model, light is thought of as a stream of zero dimensional particles of pure energy, called photons. The amount of energy in each of these photons in a certain beam of light is proportional to the frequency of that light under the wave model. E=hf E=energy of one photon h=Planck’s constant f=frequency of the light wave

Atomic Spectra Each element on the periodic table has a unique spectral “fingerprint.” These are emission spectra. Absorption spectra look like the “negative” of these.

Absorption Spectra Just so you can see the relationship, here are the absorption and emission spectra for Hydrogen:

What causes those lines? Each line corresponds to a specific frequency of light. Each frequency of light corresponds to a specific photon energy. Each specific photon energy corresponds to a different electron energy level jump in the orbital shells of that type of atom.

Electron Orbital Shells Remember the Bohr Model of an atom from Chemistry or ICP? Each ring in the model represents a different energy state that the electrons can occupy. The outer rings represent higher energy states than the inner rings. Each ring has a “quantum number” starting with n=1 at the center.

What are emission and absorption? When an electron absorbs a photon, it jumps up from a lower energy level to a higher one. When an electron emits a photon, it jumps down from a higher energy level to a lower one. http://www.youtube.com/watch?v=fKYso97eJs4

Representing the Energy Levels of an Atom Below is the Energy Diagram for a hydrogen atom. Each jump between two energy levels corresponds to a different spectral line. n=infinity is the ionization energy for this atom. This means that if an electron in the ground state absorbs a photon with that much energy it will be freed from the atom.