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

2. 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. Spectral Lines – Cassiopeia Project

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

17. Demonstration Gas Tubes (He, Hg, Ne) and Diffraction Grating

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. The specific energies (wavelengths, frequencies) of visible light absorbed and released produce the spectra.

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

21. What Causes the Aurora High speed energetic particles collide with atoms in Earth's atmosphere to cause the aurora. These high speed particles, which are usually electrons, originate from space, specifically from the solar wind, blowing outward from the Sun. When the electrons from space strike an atom or molecule in Earth's atmosphere, they give one of the electrons in the atom an energy boost. In scientific jargon, the electron jumps to a higher energy level and the atom is in an excited state.

22. What Causes the Aurora After a while, the electron in the excited atom jumps back down to its original lower energy level. It releases this energy as light causing the auroral glow. This process is the same mechanism that causes emission line spectra and aurora are in fact emission line spectra of the atoms in Earth's upper atmosphere. The color of emission line spectra depends on the type of atom that is excited, and each type of atom produces its own unique pattern of colors. Hence, the different colors in auroral displays originate from different elements in Earth's atmosphere.

23. What Causes the Aurora Oxygen molecules cause the green Aurora, and oxygen atoms cause the red colors. Blue auroral displays result from nitrogen molecules. Molecular nitrogen and oxygen are the most common constituents of Earth's atmosphere, so these are the most common auroral colors. Mixtures of these colors form the other colors of the auroras.

24. Northern Lights Video

25. Star Finder Video - Fingerprints of Light

26. Homework Chapter 4: Worksheet 3