Chapter 7. Starlight and Atoms.

1. Remember the structure of an atom (nucleus with protons and neutrons plus electron cloud orbiting the nucleus)

2. What is meant by neutral, ionized, electron shells. Remember that all normal matter consists of atoms. Each atom consists of a nucleus with electron(s) in orbit around the nucleus. The nucleus consists of proton(s) and neutron(s). Know what is meant by atomic number and atomic weight. What is an isotope? How are the chemical elements labeled?

3. The Coulomb force binds the electrons to the nucleus.

4. The various orbits around the nucleus are called energy levels because it takes energy to move away from the nucleus or the atom must give up energy for the electron to jump back toward the nucleus. Remember that only certain energies (distances from the nucleus) are permitted.

5. What is an excited atom? Ground state?

6. Know Kirchhof’s Laws as given on page 132: (1) A hot solid or dense gas produces a continuous spectrum. (2) A low density excited or hot gas produces a bright, emission line spectrum. (3) Put a low density gas in front of a continuous spectrum and you get a continuous spectrum with dark, absorption lines superimposed.

7. Know emission and absorption lines and where and how they are formed.

8. Skip the Balmer Thermometer

9. Know the Spectral Classes –especially Table 7-1.

10. What is the most abundant element in stars? Where are most of the chemical elements produced?

11. What is the Doppler Effect or Doppler Shift. How can we use it to tell whether an object is moving toward or away from us? What is meant by a blue shift? A red shift?

12. Review the use of the Doppler effect as I discussed in class.

13. Skip Shapes of Spectral Lines