1. What do the following have in common?

3. Scientific Modeling Makes scientific concepts easier to understand or visualize by referencing common knowledge Can you think of any scientific models?

4. Scientific Models

6. Models of the Atom

7. History of the Atom

8. Jigsaw Activity Number off 1-5 (4 groups of 5, 1 group of 6) Each group will be responsible for a section of the atomic theory from Hebden p.139-144 As a group, you must fully understand your section because each member will be teaching it to the rest of the class individually

9. Jigsaw Activity Group A: each member will teach the rest of the class about “Early Models of the Atom” Group B: each member will teach the rest of the class about “Dalton’s Atomic Theory” Group C: each member will teach the rest of the class about “The Thomson Model” Group D: each member will teach the rest of the class about “The Rutherford Model” Group E: each member will teach the rest of the class about “The Bohr Model"

10. Jigsaw Activity 10 min to read & make notes on the section you’re responsible for Then, all the 1s, 2s, etc. will form groups and teach new group members about their section (like piecing together a jigsaw puzzle) Each member presents 2 min on their topic starting with group A

11. Early Models of the Atom 5 th century BC - Leucippus & Democritus – Atoms are tiny, uncuttable particles – Properties are direct results of differences in size & shape of atoms

12. Early Models of the Atom 4 th century BC – Aristotle – Matter had no properties on its own – Properties came from different combinations – 4 elements: water, air, fire, earth

13. Dalton’s Atomic Theory Law of Definite Proportions E.g. 2/18 of the mass of H 2 O is always from H and 16/18 is from O Law of Multiple Proportions Compounds are made of atoms in whole number ratios E.g. H & O can make OH -, H 2 O, H 3 O +, H 2 O 2 Law of Conservation of Mass Mass of reactants = mass of products

14. Thomson’s Model of the Atom Discovered + and - particles in atoms Proposed “plum pudding” model: negatively charged raisins spread around positively charged bread

15. Rutherford Model of the Atom Gold Foil Experiment Fired alpha (He 2+ ) particles at thin gold foil Thomson model predicts minimal deflection of alpha particles b/c + charge spread out Rutherford found small fraction of particles w/ significant deflection Concluded + charges must be concentrated in a small area w/in atoms

16. Rutherford Model of the Atom

17. Bohr’s “Planetary” Model Electrons orbit around nucleus at specific energy levels Been disproven but many key ideas still apply to the modern model of the atom

18. Heisenberg’s “Cloud” Model Heisenberg’s Uncertainty Principle: σ x σ p ≥ ħ/2 The more precisely you know the position of an electron, the less precisely you know the momentum and vice versa Can’t know both at the same time so the position of electrons can only be in terms of probability