Every time you flick a lighter, those bright sparks fly because of cerium. This soft, silvery metal is so reactive that its shavings catch fire on their own. It was named after Ceres — a dwarf planet discovered just two years before the element itself.
Cerium is the most abundant rare earth element. There's more of it in Earth's crust than copper or tin. Half of all cerium mined goes into car catalytic converters. The rest ends up in glass polishing, metal alloys, and UV protection coatings.
Today cerium plays two starring roles in industry. First, every car with a catalytic converter carries 1–2 grams of cerium. Its oxide CeO₂ traps poisonous carbon monoxide and converts it into harmless CO₂. Second, cerium oxide is the world's best glass polishing powder — nothing else gives such a flawless surface.
Scientists are also exploring CeO₂ nanoparticles as medical antioxidants. They can neutralize free radicals inside cells. In the future, cerium might help treat diseases linked to aging.
Metallic cerium is pyrophoric: powder and shavings ignite spontaneously at just 150–180 °C. Store it under inert gas (argon). Cerium dust clouds can explode. Cerium compounds have low toxicity, but inhaling CeO₂ nanoparticles over time can cause lung buildup. Required protection: respirator, gloves, and good ventilation.
Lighter sparks come from cerium. Mischmetal (50% cerium) heats to 3,000 °C when scraped against steel. That's why tiny particles burst into bright sparks.
Cerium is named after the dwarf planet Ceres. Astronomer Piazzi discovered Ceres in 1801. Just two years later, chemists found a new element and honored the discovery.
Cerium oxide polishes glass at the atomic level. Particles just 1–5 micrometers wide simultaneously grind and chemically dissolve imperfections. The result is a perfectly smooth surface.
Cerium blocks UV light. Glass treated with CeO₂ stops harmful ultraviolet radiation. That's why it's used in sunglasses and museum display cases.
"Rare" is misleading. Earth's crust contains 66 mg/kg of cerium — more than copper (60 mg/kg). It got the "rare earth" label only because it's hard to separate from other lanthanides.
Cerium can "breathe" oxygen. Its oxide switches between Ce³⁺ and Ce⁴⁺ states, absorbing and releasing oxygen on demand. That's what makes it such a powerful catalyst.
| Isotope | Mass (u) | Abundance | Half-life | Decay |
|---|---|---|---|---|
136Ce | 135.907172 | 0.18% | stable | — |
138Ce | 137.905991 | 0.25% | stable | — |
140Ce | 139.905439 | 88.45% | stable | — |
142Ce | 141.909244 | 11.11% | stable | — |
Analysis of cerite