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 Chemistry1. 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

My ModelThe Atom The Electron

•Atomism–Pre-socratics/Aristotle

•Dalton–The “modern” atomic theory

•Thomson–electron/plum pudding model

•Becquerel/Curie/radioactivity

•Rutherford–Nucleus/Gold Foil experiment

•Millikan–qe/”oil drop” experiment

•Nuclear transformations–Rutherford again (transmutations)–Decay modes

•Light as a wave

•Kirchoff/Bunsen–Emission spectra

•Balmer/Rydberg

•Planck–Development of quantum concept–Blackbody emitters–“ultraviolet catastrophe”*

•Bohr Model

•Schrödinger Model–Electron configurations–orbital diagrams

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…

19001600 1700 1800 1915 1930

Light theory

Electron Theory

Thomson (JJ) discovers electron

Newton proposes particle theory of light

Huyghens’ Principle supports waves

Hooke proposes wave theory

Young: 2-slit experiment shows wave behavior

Faraday suggests electricity and magnetism related

Maxwell’s Equations relate light, electricity, magnetism

Hertz detects radio waves (supports wave theory)

Planck puts idea in Einstein’s head

Photoelectric Effect (supports particle interpretation –Einstein relates to Planck’s quanta concept)

Balmer, Rydberg relate emission spectrum lines to counting number “n”

Bohr Model proposed

De Broglie proposes matter has wave-like qualities

Heisenberg Uncertainty Principle

Schrödinger Wave Model

Davisson/G.P. Thomson (irony!): electron diffraction

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

Choose The Form!

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

Max Born ErnestMarsden

JamesChadwick

HansGeigerHenry

MoseleyNiels Bohr

Robert Millikan

Ernest Rutherford

PhilippLenard

ErwinSchrödinger

MaxPlanck

WolfgangPauli

FriedrichHund

WernerHeisenberg

Louisde Broglie

AlbertEinstein

JJ Thomson

CambridgeManchester

Berlin

Göttingen

Copenhagen

Resources

Powerpoint presentations:• Early Atomic Structure•The Bohr Model•The Schrödinger Model (quantum numbers by element)