Objectives

You have completed this lesson when you can:

1. Define "atomic mass units" (amu) and relate them to isotopic masses, atomic masses, and formula masses.

2. Conceptually define Avogadro's Number. Know its value. Distinguish between its definition and its measurement.

3. Use Avogadro's Number to calculate the number of atoms or molecules from mass or moles (and vice versa).

4. In general, relate how various studies and discoveries having to do with light, electricity and radioactivity challenged Dalton's model of atoms and converged to give us our current model of atomic structure, including:

   • Describe how the work of Volta and Faraday gave evidence for the electrical nature of atoms.

   • Describe cathode rays and what they told us about electrons. Describe positive rays and what they told us about the mass of atoms.

   • Describe mass spectrometry and how it added to our understanding of atomic weights and isotopes.

   • Describe how the study of radioactivity led to the discovery of isotopes and to the conclusion that some atoms could break apart.

   • Describe Rutherford's alpha-scattering experiments and how they led to the discovery of atomic nuclei and the creation of the nuclear model of atoms.

5. Describe the internal composition and structure of various atoms, ions and isotopes including the variations that relate atoms to ions and isotopes, including:

   • Describe the size, mass and charge of protons, neutrons and electrons.

   • Describe the arrangement of protons, neutrons and electrons in atoms.

   • Explain what ions are in terms of protons, neutrons and electrons.

   • Write and interpret (not predict) formulas for ions.

   • Explain what isotopes are in terms of protons, neutrons and electrons.

   • Define "atomic number" and "mass number" in terms of protons, neutrons, and electrons.

   • Write and interpret isotopic symbols.

6. Describe how atomic spectra gave evidence of energy levels in atoms. Distinguish between continuous and line spectra and between absorption and emission spectra.

7. Describe the Bohr model of atoms and how it explains atomic spectra.

8. Describe the arrangement of electrons in atoms using the Bohr model.

9. Describe the arrangement of electrons in atoms using the "orbital model", which is also called the "wave mechanical model."