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Atomic Structure Teaching Resources. Eric Grunden Raleigh Charter High School Raleigh, NC. What’s Important?. Chemistry EOC (not that this matters anymore…) 2.01 Analyze the historical development of the current atomic theory. Early contributions: Democritus and Dalton.
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Atomic Structure Teaching Resources Eric Grunden Raleigh Charter High School Raleigh, NC
What’s Important? • Chemistry EOC (not that this matters anymore…) • 2.01 Analyze the historical development of the current atomic theory. • Early contributions: Democritus and Dalton. • The discovery of the electron: Thomson and Millikan. • The discovery of the nucleus, proton and neutron: Rutherford and Chadwick. • The Bohr model. • The quantum mechanical model. • 2.02 Examine the nature of atomic structure. • Subatomic particles: protons, neutrons, and electrons. • Mass number. • Atomic number. • Isotopes.
What’s Important? • AP Chemistry 1. Evidence for the atomic theory 2. Atomic masses; determination by chemical and physical means 3. Atomic number and mass number; isotopes 4. Electron energy levels: atomic spectra, quantum numbers, atomic orbitals 5. Periodic relationships including, for example, atomic radii, ionization energies, electron affinities, oxidation states
The Atom • Primary Documents • Dalton reading • Simulations • Gold Foil Experiment (requires Java –standalone/web) • The APE MAN! • Atomic Number = Protons = Electrons • Mass Number = Atomic Number + Neutrons
Primary Documents! • Be the envy of your Social Science colleagues! • Dalton’s A New System of Chemical Philosophy(suitable for moderate readers) • Bohr’s On the Constitutions of Atoms and Molecules(very readable, though complex; complete with math for the truly adventurous) • Others available by search or from the Chemteam website. • Excerpting is the way to go • Pair students and have them explain passages to each other • Scalable up to more advanced students
The Electron • Challenging Concepts! • Revolutionary period – not “normal science” • Highly abstract nature • Cognitive dissonance is good! • History of Light and electrons are intertwined…
Light theory Faraday suggests electricity and magnetism related Photoelectric Effect (supports particle interpretation –Einstein relates to Planck’s quanta concept) Newton proposes particle theory of light Hooke proposes wave theory Maxwell’s Equations relate light, electricity, magnetism Huyghens’ Principle supports waves Hertz detects radio waves (supports wave theory) De Broglie proposes matter has wave-like qualities Young: 2-slit experiment shows wave behavior Planck puts idea in Einstein’s head 1600 1700 1800 1900 1915 1930 Thomson (JJ) discovers electron Heisenberg Uncertainty Principle Balmer, Rydberg relate emission spectrum lines to counting number “n” Bohr Model proposed Davisson/G.P. Thomson (irony!): electron diffraction Schrödinger Wave Model Electron Theory Pauli Exclusion Principle
Content Highlights • Observation of spectra without explanation (Kirchoff/Bunsen) • Balmer/Rydberg develop a mathematical relationship without an explanation • Quantization of energy required as a concept
Quantum Mythbusting • There was no “ultraviolet catastrophe” • Term not coined until 1911 • There was a disagreement between theory and observation, but no catastrophe • Planck did not quantize light • Einstein did this later
Content Highlights, con’t • Wave-Particle Duality • Einstein suggests that photoelectric effect results can only be explained if light behaves like a particle • Quantum Indeterminacy • Objects exist in indetermined states until observed • Schrödinger’s Cat • Ghostbusters
Content Highlights, further! • Hund’s Rule = Monopoly houses • Balmer/Rydberg develop a mathematical relationship without an explanation • Quantization of energy required as a concept
Simulations Bohr Model Applet (web) Electron Model Comparison (requires Java –standalone/web) Orbital Viewer (standalone, downloadable)
Labs • Hydrogen Spectrum Lab(h/t Mike Jones, Pisgah HS) • Flame Tests • DON’T use petri dishes, spray bottles, dry salts (safety/toxicity concerns) • Try instead • Wooden splints (steal from coffee shops); soak in • Aqueous solutions of salts (plus a little MeOH): LiCl, KCl (if you have cobalt glasses), CaCl2, SrCl2, boric acid (for green; I avoid Ba salts) • Fireworks glasses (rainbow glasses)
The Atomic Theory Org Chart It’s not just what you know, but apparently whom
Niels Bohr JJ Thomson Friedrich Hund Werner Heisenberg Ernest Rutherford Henry Moseley Wolfgang Pauli Erwin Schrödinger Robert Millikan Ernest Marsden James Chadwick Louis de Broglie Hans Geiger Max Planck Philipp Lenard Albert Einstein Manchester Cambridge Copenhagen Max Born Göttingen Berlin
Resources • Powerpoint presentations: • Early Atomic Structure • The Bohr Model • The Schrödinger Model (quantum numbers by element)