1. Electron Energy and Radiation Quantum Mechanics and Electron Movement

2. Bohr’s model Helped explain why elements give off certain colors of light (excited electrons jumping to lower energy levels) Electrons travel in specific energy “orbits” but not in between them. 1st 2nd 3rd Electron can be here But not here

3. Ground state: All the electrons in an atom have the lowest possible energies (Aufbau Rule!) Most stable electron configuration Li  1s 2 2s 1 Excited State: Electron(s) have absorbed energy & are in now in an higher energy orbital Li  1s 2 (2s 0 2p 0 ) 3s 1 Electron Jumped from n=2 to n=3 Very unstable  Electron(s) will return to its original state. Gives off energy as a photon Electron Configuration

4. Question Why do elements give off different colors of light when heated? Hint: What is unique about each element?

5. Emission Spectrum Each element has a different “energy staircase” i.e. unique electron movement pattern As they move between energy levels, electrons absorb or emit specific amounts of energy Amount of energy corresponds to specific wavelengths (colors) of light. Emission spectrum: unique series of emitted colors enables us to identify elements based on their energy emission.

6. Spectra Each element has a characteristic pattern of light that it emits. This can be used as a “fingerprint” for identification.

8. Red. Orange. Yellow. Green. Blue. Indigo. Violet Long wavelength Short wavelength Less Energy Greater Energy Red Orange Yellow Green Blue Indigo Violet

9. EMR or crests Equal to the amount of Energy Frequency - # of wave cycles to pass a given point per unit of time (Hz or s -1 ) Symbol (m)

10. EMR (Electromagnetic Radiation) All wavelengths = from gamma rays (very short=high energy) to radio and TV (long=low energy).

11. EMR (Electromagnetic Radiation) All types of EMR travel at the speed of light Product of Frequency & Wavelength ALWAYS equals a constant  the speed of light (c) c = vc = 2.998 x 10 8 m/s or 3.00 x 10 8 m/s A “piece” or quanta of EMR is called a photon. Energy  E­ photon = h v Plancks Constant  h = 6.626 x 10 -34 J s

12. Review EMR waves or crests Solving problems Show all your work, write the equation and be sure to indicate your units 1) What is the wavelength of electromagnetic radiation with a frequency of 8.77 x 10 14 Hz? 2) What is the frequency of light that has a wavelength of 400. nm?