1. The Bohr Model of the Atom
Chapter 4
The Bohr Model of the Atom

3. Visible Light

4. Niels Bohr
In 1913 Bohr published a theory about the structure of the atom based on an earlier theory of Rutherford's.
Bohr expanded upon this theory by proposing that electrons travel only in certain successively larger orbits.

5. Bohr Model of the Atom
Electrons orbit the nucleus in orbits that represent specific quantities of energy.
The energies of the electrons in the atom are quantized.
Only certain electron orbits (energy levels) are allowed.
The Bohr Atom

6. Niels Bohr
Bohr also described the way atoms emit radiation by suggesting that when an electron jumps from an outer orbit to an inner one, that it emits light.

7. Ground State
The lowest energy state of an atom.

8. Excited State
Any energy state of an atom that is higher in energy than the ground state.

9. Energy Absorbed

10. Absorption (Dark – Line) Spectra

11. Energy Emitted
Electron jumps to a lower orbit

12. Emission (Bright – Line) Spectra

13. Emission Spectra

14. The lines present in an emission spectrum are the lines missing in an absorption spectrum.

16. Demonstration Diffraction Grating and White Light
Gas Tubes (He, Hg, Ne) and Diffraction Grating

17. Spectroscopy Part 1

19. Describe the process that occurs inside atoms that produces the spectra?
Energy is absorbed by the atom.
The electrons jump into higher orbits and the atom becomes “excited”.
The electrons return to their original orbits and the atom returns to the ground state.
The electrons release energy in the form of visible light.
Each “quantum leap produces a different energy (wavelength, frequency) of visible light which accounts for each different spectral line.

20. Homework Chapter 4: Worksheet 2 (due tomorrow).
Lab Summary: Flame Tests (due Thursday).
Study Guide Chapter 4 (due Friday).

21. Chapter 4
Spectroscopy
Part 1

23. Quantum Leaps
A quantum leap is a change of an electron from one energy state to another within an atom.
Quantum leaps cause the absorption and emission of electromagnetic radiation in which “excited” atoms release small packets of electromagnetic energy called photons.

24. Some Uses and Examples of “Exciting” Atoms (Quantum Leaps)
Aurora Borealis (The Northern Lights)

25. Northern lights (Aurora’s) are one of nature's most beautiful manifestations of the ability of electrons to jump between quantum states

26. Northern Lights Video (3:57)

27. Aurora Borealis

28. Did you ever wonder how we know what the universe is made of?

29. The entire article is posted near the door of the classroom if you would like to read more.

30. Star Finder Video - Fingerprints of Light (10:05) Full Video (13:50)

31. Homework (All due Tuesday)
Summarize the purpose and procedure for the “Flame Test” Lab.
Chapter 4 Worksheet 3.
Study Guide Chapter 4.