Quick Facts
| Property | Value |
|---|---|
| Symbol | Ce |
| Atomic Number | 58 |
| Atomic Mass | 140.12 u |
| Category | Lanthanide |
| Period | 6 |
| Group | 3 |
| Block | f |
| Electron Configuration | [Xe] 4f¹ 5d¹ 6s² |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 6.770 g/cm³ |
| Melting Point | 799°C (1072 K) |
| Boiling Point | 3443°C (3716 K) |
| Appearance | Silvery-white, soft metal |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Xe] 4f¹ 5d¹ 6s² |
| Electronegativity | 1.12 (Pauling scale) |
| First Ionization Energy | 534.4 kJ/mol |
| Atomic Radius | 182 pm |
| Covalent Radius | 204 pm |
| Van der Waals Radius | 235 pm |
History and Discovery
Discovered by: Jöns Jacob Berzelius and Wilhelm Hisinger; Martin Heinrich Klaproth Year of Discovery: 1803 Location: Sweden and Germany
Etymology
Named after the asteroid Ceres, which was discovered in 1801, two years before cerium itself.
Discovery Story
Cerium was discovered independently in 1803 by Jöns Jacob Berzelius and Wilhelm Hisinger in Sweden, and by Martin Heinrich Klaproth in Germany. They analyzed a mineral from Bastnas, Sweden (later called cerite). Carl Gustaf Mosander later showed that cerium oxide contained other elements (lanthanum and didymium).
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ¹³⁶Ce | 0.19% | Stable | - |
| ¹³⁸Ce | 0.25% | Stable | - |
| ¹⁴⁰Ce | 88.45% | Stable | - |
| ¹⁴²Ce | 11.11% | >5 × 10¹⁶ years | β⁻β⁻ |
Occurrence
Natural Abundance
Cerium is the most abundant rare earth element, comprising about 66 ppm of Earth's crust—more abundant than copper. Found in bastnasite and monazite ores. Major producers are China, the United States, and Australia.
Extraction and Production
- Solvent Extraction: From rare earth concentrates
- Reduction: Of cerium fluoride with calcium
- Sources: Bastnasite and monazite mining
- Cerium is about 50% of rare earth production
Applications and Uses
Catalysts
- Automotive catalytic converters (cerium oxide)
- Petroleum refining catalysts
- Self-cleaning ovens
Glass and Ceramics
- Glass polishing (cerium oxide is the primary polishing agent)
- UV-absorbing glass
- Decolorizing glass
Metallurgy
- Steel desulfurization
- Aluminum and iron alloys (mischmetal)
- Nodular cast iron production
Other Uses
- Lighter flints (mischmetal—about 50% cerium)
- Solid oxide fuel cells
- Sunscreen (cerium dioxide nanoparticles)
- Phosphors
Biological Role
Cerium has no known biological role.
In the Human Body
Cerium is not normally found in the body. It has low toxicity but may accumulate in bones and liver.
Safety and Hazards
Toxicity
Cerium has low toxicity. Cerium oxide nanoparticles are under investigation for potential health effects.
Handling Precautions
- Cerium metal is pyrophoric (ignites spontaneously when finely divided)
- The spark from lighter flints is burning cerium
- Store under inert atmosphere
- Handle with fire precautions
Environmental Impact
Rare earth mining has environmental impacts. Cerium is relatively abundant and widely used.
Interesting Facts
- Cerium is the most abundant of all rare earth elements
- Lighter flints work because cerium is pyrophoric—it sparks easily
- Cerium oxide is the standard glass polishing compound worldwide
- It can exist in +3 or +4 oxidation states (unusual for lanthanides)
- Cerium was named after the asteroid Ceres, which was itself named after the Roman goddess of agriculture