Lecture 11. F. Spectral Lines
Electrons can orbit atoms with different amounts of energy -- but only certain
"allowed" energies, called ENERGY LEVELS or ORBITALS. No e-'s can orbit atoms with energies between
allowed levels.
- Why? Don't ask me, I only work here...
- A good analogy is with an elevator -- it only stops at floors,
not between them.
e-'s can change levels by absorbing or emitting a photon
- ABSORPTION increases energy: e-'s move up
- EMISSION decreases energy: e-'s move down
there are minimum and maximum levels:
- the lowest energy level is the GROUND STATE -- no allowed energies below it
- if an e- absorbs a photon of too much energy, it leaves orbit, IONIZING the atom
according to the principle PAULI EXCLUSION,
orbitals can be full -- meaning an e- cannot move into the full orbital,
even if it has the correct energy
Each element has its characteristic arrangement of energy levels
- photons emitted by e-'s moving among these levels have
's and f's characteristic of these
energies
- so emission/absorption photons show a characteristic SPECTRUM,
according to which element formed them
- this info. can be used to determine elements present in distant objects -- e.g., He on Sun
- (thermal photons do not contain any information about which element formed them)