1. 1 Chemistry 111 Sections 5.1 – 5.8 Chemistry 111

2. 2 Chapter 5 Chapter 5 Topics –Atom Concept (Dalton) –Protons, neutrons & electrons –Nuclear Atom (Rutherford) –Isotopes, Nuclear symbols –Atomic Mass & Average Atomic Mass –Periodic Table (Mendeleev) –Elemental Symbols What we’ll do: –Discuss Figures 5.3 & 5.4 (Rutherford) –Quick Review of Nuclear Symbols –Average Atomic Mass (Mathy) –Review your chapter notes, work on Homework.

3. 3 Rutherford Experiment Before: –Thompson’s Plum Pudding Model of the Atom pudding = positively charged matter plums = electrons –Atoms are solid chunks with (+) stuff & electrons (-). + + + + + Pudding + Plums (e - ) = an Atom. + + + + +

4. 4 Rutherford Experiment II Experiment: –Shoot alpha particles (2+ charge) at a thin gold foil –Should burn a hole & go straight through In the lab, they saw something else…

5. 5 Rutherford Experiment Animation

6. 6 Rutherford Experiment III Results / Conclusions –Now the atom is mostly empty space –Nucleus has positive charge & most of mass. –Electrons in a diffuse cloud around the nucleus.

7. 7 Nuclear Symbols The nuclear symbol is a format we use to quickly specify a given isotope. You have to memorize the exact format: Z = atomic number = # of protons A = mass number = #p + #n Sy = elemental symbol Examples: –Radioactive Carbon 6 protons, 14-6=8 neutrons –Bomb-quality Uranium 92 protons, 235-92=143 neutrons

8. 8 Average Atomic Mass Isotopes:  12 C has Mass of A  12 amu or g/mol  Period table gives 12.011 amu or g/mol  Which is correct? Both:  Natural Earth Carbon is a mixture of 12 C, 13 C, and 14 C.  Table 5.2 shows:  12 C = 12.000000000 amu98.93 %  13 C = 13.003354826 amu1.07 %  Mass of periodic table is the weighted sum of these numbers

9. 9 Average Atomic Mass II Weighted Sum:

10. 10 Team Exercise This chapter is mainly qualitative –We will use the team activity to actively review the topics. –Discuss what you don’t fully understand. –Note topics that you want me to go over at the beginning of Thursday’s class. –Review your chapter notes. –Discuss Textbook Problems (esp. # 25, 8) –Consider an ad-hoc concept map? GOAL / ASSIGNMENT: Spend time actively reviewing the material. Complete your active learning log.