Lesson Plan

What the Emperor Ate With

1827 to 1900, Berlin, Paris, Oberlin Ohio, and Pittsburgh • Cyclotrialumane: the first stable Al(I) trimer, demonstrated in April 2026 to perform two reactions until now reserved for platinum and palladium. • May 4, 2026

Before using this lesson plan: Read the full story or listen to the 6-minute narration (works as a bell-ringer).

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Lesson Plan : What the Emperor Ate With

Subject area

STEM : chemistry, materials science, history of technology, industrial economics.

Recommended audience

High-school chemistry (Years 11-13 / Grades 10-12)

First-year undergraduate inorganic chemistry

General STEM enrichment for ages 14+

Lesson length

60-75 minutes (one period plus optional follow-up).

Learning objectives

By the end of the lesson, students will be able to:

Explain why aluminium is the third most abundant element in the Earth's crust yet was once more expensive than gold.

Describe the Hall-Héroult electrolytic process and identify why it required cheap electricity to be viable.

Compare the catalytic behaviour of platinum-group metals with the new cyclotrialumane and articulate why oxidation state matters for catalysis.

Construct a price-vs-time graph for aluminium between 1854 and 2026 and interpret the inflection point of 1886.

Discuss the economic and strategic implications of a base-metal substitute for platinum-group catalysts.

Key terms

Oxide, ore, bauxite, cryolite (Na₃AlF₆)

Reduction (chemical and electrolytic)

Electrolysis, electrode, anode, cathode

Oxidation state (Al³⁺, Al¹⁺)

Catalysis, transition metal, organometallic chemistry

Polymerisation, ethene, polyethylene

Ziegler-Natta catalysis

Cyclotrialumane, Al(I) trimer

Pre-class preparation

Bring or display a beverage can, a roll of aluminium foil, and (if available) a small ingot of aluminium.

Have a periodic table on the wall.

Optional: a piece of platinum jewellery or a printed photograph of a catalytic converter to anchor the comparison.

Lesson outline

1. Hook (5 min) : "the most precious metal at the table"

Hold up a beverage can. Ask students to estimate its retail value as raw metal. Reveal: less than half a cent's worth of aluminium. Then describe the 1855 Tuileries banquet, where Napoleon III served his most honoured guests with cutlery made of the same metal because it was at the time more expensive than gold. Pose the central question: what changed?

2. Why was aluminium so hard to extract? (10 min)

Locate aluminium on the periodic table (group 13, period 3).

Discuss the +3 oxidation state and the strength of the Al-O bond in alumina (Al₂O₃).

Sketch the electron configuration: [Ne] 3s² 3p¹. All three valence electrons depart immediately on oxidation.

Compare with iron and copper: their lower-oxidation-state oxides are reducible by carbon at modest temperatures (blast furnace, reverberatory furnace). Al₂O₃ is not.

Wöhler's 1827 synthesis: AlCl₃ + 3K → Al + 3KCl. Why this is expensive (potassium metal is itself expensive).

Sainte-Claire Deville's 1854 sodium reduction: AlCl₃ + 3Na → Al + 3NaCl. Why this scales a little but not enough.

3. The Hall-Héroult breakthrough (15 min)

1886. Two 22-23 year olds, one in Oberlin Ohio, one in Paris, file patents three months apart for the same idea: dissolve Al₂O₃ in molten cryolite (Na₃AlF₆), which lowers the effective melting point from ~2000°C to ~960°C, and pass an electric current through the bath. Aluminium metal collects at the cathode.

Half-equations:

Discussion: why was this not feasible before 1886? Answer: large-scale generators (Werner von Siemens 1866; commercial dynamos in the 1870s) were the prerequisite. Aluminium production is still the single biggest industrial consumer of electricity in the world: about 14 kWh per kilogram of metal.

Show a price-vs-time graph for aluminium 1854-1914. The price falls roughly 4000-fold in a single generation.

4. Aluminium becomes ubiquitous (5 min)

Discuss why aluminium suits beverage cans (light, ductile, oxide layer self-passivates), aircraft (strength-to-weight), foil, electrical conductors (cheaper than copper for long-distance transmission), saucepans.

Note: about 70 million tonnes of aluminium are produced globally per year. Compare with annual gold production (about 3,500 tonnes).

5. Why aluminium could not be a catalyst : until now (15 min)

Define catalysis briefly: a substance that lowers the activation energy of a reaction without being consumed.

Show a periodic table and circle the platinum-group metals (Ru, Rh, Pd, Os, Ir, Pt). These dominate industrial catalysis: catalytic converters, hydrogen splitting, polymerisation, cross-coupling reactions.

Why? Transition metals can adopt multiple oxidation states. They can hand single electrons in and out of bonds, which is exactly what catalysis requires.

Aluminium normally goes straight to Al³⁺ and stays there. It has no electrons left to give. In catalytic terms, a brick.

2026 breakthrough (Bakewell et al, Nature Communications): the first stable cyclotrialumane. Three aluminium atoms in a triangle, each in the +1 oxidation state. Two of the three valence electrons are held back by the geometry and the bulky organic groups protecting the triangle.

Demonstrated reactions:

Key teaching point: the chemistry is the same. The difference is the metal. Aluminium is roughly 20,000 times cheaper per kilogram than platinum.

6. Economic and strategic implications (10 min)

Open discussion. Catalyst chemistry is roughly a $50 billion global business, much of it tied to recycling precious metals out of reactors.

Platinum-group metal production is concentrated in two countries (South Africa, Russia). Replacing them with aluminium would change the geopolitics of catalysis.

Caveat: one paper. The team have shown the chemistry works in solution, on small scales, with bulky protecting groups. Industrial scale-up is a long road.

Closing comparison: in 1855 aluminium was the precious metal next to the crown jewels. In 2026 it is the candidate base metal that may displace the precious metals in the catalysts that build the modern world.

7. Wrap and assignment (5 min)

Pose: "If aluminium catalysis scales, what changes about the way we make plastics, fuels, and pharmaceuticals?"

Optional homework: draw the cyclotrialumane molecule (3 Al atoms in a triangle, each with one bulky aryl group). Label the oxidation state and identify how many valence electrons each aluminium retains. Which platinum-catalysed reaction would you most want to replace with this chemistry, and why?

Discussion questions

Why does the strength of a chemical bond determine the cost of a metal? Use Al₂O₃ as your example.

The Hall-Héroult process required two technologies to coexist: molten-salt electrolysis and large-scale electricity generation. How does this illustrate the dependence of one technology on another?

Aluminium and gold both appear inert in everyday life. Why was one always cheap and the other always precious, given that aluminium was once more valuable than gold?

What does it mean for a metal to "have electrons left to give"? Why does this matter for catalysis?

The cyclotrialumane needs bulky organic groups to remain stable. What problem do those groups solve, and what new problem might they introduce when you try to scale the process?

Both Charles Hall and Paul Héroult were 22 or 23 years old in 1886, working without supervision in modest laboratories, and they made the same discovery within three months. What does this tell you about how scientific breakthroughs happen?

Extension activities

Lab demonstration (where facilities allow): electrolysis of a copper sulfate solution to illustrate the principle of electrochemical reduction. (Aluminium electrolysis itself is not safely demonstrable in a school setting; the cryolite bath is at 960°C.)

Calculation: estimate the energy cost of producing 1 kg of aluminium at 14 kWh/kg using your local electricity tariff. Compare with the wholesale market price of aluminium ($2/kg in 2026).

Research project: build a timeline of breakthroughs in industrial catalysis from Berzelius (1835) to the present, and identify three other reactions where a base-metal catalyst has recently displaced or may soon displace a precious-metal catalyst.

Writing assignment: write a 500-word newspaper-style article reporting the cyclotrialumane discovery to a non-scientific audience. Include one quote from Dr Bakewell and one from a sceptical industrial chemist.

Time Rhymes