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TOPIC: THE NATURE OF ATOMS INTRODUCTION In this lesson we will explore the structure of the atom. In particular, we will focus on two areas of atomic structure, mass and charge. We use information about the mass of atoms to tell us about the quantities of chemicals - how much we have, how much of one reacts with how much of another, how much product is formed in a reaction, and so forth. It will be especially important for us to be able to relate the mass of a chemical sample to the number of atoms or molecules it contains. This area of chemistry is sometimes called "stoichiometry." We use information about the charged particles in atoms to help us understand the physical and chemical properties of materials. Their physical properties include such things as melting and boiling points, volatility, what solvents they dissolve in, and so on. Their chemical properties describe what chemical reactions they undergo and why.
PURPOSE: To help you become familiar with the development of atomic theory and with a model of atomic (and electronic) structure.
OBJECTIVES: You have completed this lesson when you can: 1. Define "atomic mass units" (amu) and relate them to isotopic weights, atomic weights, and formula weights. 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. (For important specifics, see objectives 5-9, 18-21.) 5. Describe how the work of Volta and Faraday gave evidence for the electrical nature of atoms. 6. Describe cathode rays and what they told us about electrons. Describe positive rays and what they told us about the mass of atoms. 7. Describe mass spectrometry and how it added to our understanding of atomic weights and isotopes. 8. Describe how the study of radioactivity led to the discovery of isotopes and to the conclusion that some atoms could break apart. 9. 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. 10. Describe the internal composition and structure of various atoms, ions and isotopes including the variations that relate atoms to ions and isotopes. (For important specifics, see obj. 11-17.) 11. Describe the size, mass and charge of protons, neutrons and electrons. 12. Describe the arrangement of protons, neutrons and electrons in atoms. 13. Explain what ions are in terms of protons, neutrons and electrons. 14. Write and interpret (not predict) formulas for ions. 15. Explain what isotopes are in terms of protons, neutrons and electrons. 16. Define "atomic number" and "mass number" in terms of protons, neutrons, and electrons. 17. Write and interpret isotopic symbols. 18. Describe how atomic spectra gave evidence of energy levels in atoms. Distinguish between continuous and line spectra and between absorption and emission spectra. 19. Describe the Bohr model of atoms and how it explains atomic spectra. 20. Describe the arrangement of electrons in atoms using the Bohr model. 21. Describe the arrangement of electrons in atoms using the "orbital model", which is also called the "wave mechanical model."
E-mail instructor: Eden Francis Clackamas Community College
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