What do the following have in common?. Scientific Modeling Makes scientific concepts easier to...
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Transcript of What do the following have in common?. Scientific Modeling Makes scientific concepts easier to...
What do the following have in common?
What do the following have in common?
Scientific Modeling
• Makes scientific concepts easier to understand or visualize by referencing common knowledge
• Can you think of any scientific models?
Scientific Models
Scientific Models
Models of the Atom
History of the Atom
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
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"
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
Early Models of the Atom
• 5th century BC - Leucippus & Democritus– Atoms are tiny, uncuttable particles – Properties are direct results of differences in size
& shape of atoms
Early Models of the Atom
• 4th century BC – Aristotle– Matter had no properties on its own– Properties came from different combinations– 4 elements: water, air, fire, earth
Dalton’s Atomic Theory
Law of Definite Proportions• E.g. 2/18 of the mass of H2O is always from H and
16/18 is from OLaw of Multiple Proportions • Compounds are made of atoms in whole number
ratios • E.g. H & O can make OH-, H2O, H3O+, H2O2
Law of Conservation of Mass• Mass of reactants = mass of products
Thomson’s Model of the Atom
• Discovered + and - particles in atoms • Proposed “plum pudding” model: negatively
charged raisins spread around positively charged bread
Rutherford Model of the Atom
Gold Foil Experiment• Fired alpha (He2+) 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
Rutherford Model of the Atom
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
Heisenberg’s “Cloud” Model
• Heisenberg’s Uncertainty Principle: σxσp ≥ 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