Cerium
Cerium is a soft, iron-gray metal and, despite the "rare earth" label attached to its chemical family, it's actually the most abundant of all the rare-earth elements. It's best known for its role in polishing glass to an exceptionally fine finish and for sparking the flame in many lighters.
- Group · Period
- — · 6
- At room temp
- solid
- Melts at
- 1071 K
- Density
- 6.77 g/cm³
- Discovered
- 1803
Uses
Cerium oxide’s most valuable property is as a polishing compound: it removes material from glass surfaces both mechanically and through a mild chemical reaction, producing an exceptionally smooth finish that’s become the industry standard for polishing optical lenses, mirrors and glass screens. Cerium compounds also play a role in catalytic converters, where they help oxidize pollutants in vehicle exhaust more completely, and in self-cleaning oven coatings, where a catalytic layer helps burn off cooked-on residue at high temperatures.
Alloyed with iron and other rare-earth elements into mischmetal, cerium is also the spark-producing material used in the flints of many lighters and some industrial ignition devices.
History
Cerium was discovered in 1803, identified independently by Swedish chemists Jöns Jacob Berzelius and Wilhelm Hisinger and, separately, by German chemist Martin Heinrich Klaproth, both groups finding it in a heavy mineral later named cerite. It was named after Ceres, the dwarf planet that had itself been discovered just two years earlier in 1801, continuing a tradition of naming new elements after recently found astronomical objects. Cerium went on to become the first rare-earth element widely understood, and its relative abundance has made it, ever since, the most commercially significant member of that entire chemical family.
Fun facts
- Cerium is the most abundant of all the rare-earth elements, more common in the Earth's crust than copper.
- Cerium oxide is the standard polishing compound used to finish fine glass, mirrors and camera lenses to an extremely smooth surface.
- The sparking flint in many lighters is made from mischmetal, an alloy that's mostly cerium mixed with iron and other rare-earth metals.
Frequently asked questions
If cerium is a 'rare earth,' why is it so abundant?
The term "rare earth" is a historical label, not an accurate description of how scarce these elements actually are — it dates back to when they were first identified in uncommon minerals and were hard to separate from one another chemically. Cerium in particular is more abundant in the Earth's crust than many familiar metals, including copper, so the "rare" in rare earth refers more to how they were found than to how much of them exists.
What is cerium oxide used for in polishing?
Cerium oxide is unusually effective at polishing glass because it doesn't just abrade the surface mechanically — it also reacts chemically with the glass in a way that smooths it more evenly than most other polishing compounds can. That combination makes it the standard choice for finishing high-precision optics like camera lenses, telescope mirrors and glass components in electronics.
Why is cerium used in lighter flints?
The sparking flints found in many lighters aren't pure cerium but an alloy called mischmetal, made mostly of cerium along with other rare-earth metals and a little iron. When the flint is scraped, tiny shavings of this alloy ignite instantly in air because of how readily the metal oxidizes, throwing off the shower of sparks that lights the fuel.
Compounds
5 notable compounds containing Ce
- (NH4)2Ce(NO3)6reagent
Ceric ammonium nitrate
An orange-red crystalline salt and one of chemistry's most reliable single-electron oxidants, widely known simply as CAN in organic synthesis labs.
Used for: Oxidizing reagent in organic synthesis and printed-circuit etching
- CeCl3halide
Cerium(III) chloride
A white, hygroscopic salt that is the standard entry point into cerium(III) chemistry and a mild Lewis acid used to tame reactive organometallic reagents.
Used for: Lewis acid additive in organic synthesis (Luche reduction)
- Ce2O3oxide
Cerium(III) oxide
A blue-green oxide that readily picks up oxygen from air to become cerium(IV) oxide, illustrating how easily cerium swings between its two common oxidation states.
Used for: Precursor in cerium oxide production and glass-polishing formulations
- CeO2oxide
Cerium(IV) oxide
A pale yellow oxide, also called ceria, that showcases cerium's unusually accessible +4 state and its knack for shuttling oxygen atoms in and out of its crystal lattice.
Used for: Catalytic converter component and glass/optical-lens polishing compound
- Ce(SO4)2reagent
Cerium(IV) sulfate
A yellow-orange oxidizing salt, also called ceric sulfate, whose precisely standardized solutions are a workhorse titrant in analytical chemistry.
Used for: Oxidimetric titrant in analytical chemistry (cerimetry)
Isotopes
38 known isotopes
Swipe to see all columns →
| Isotope | Natural abundance | Half-life | Decay mode | Mass excess | Binding energy / nucleon | Decay width |
|---|---|---|---|---|---|---|
| Ce-136 stable | 0.186% | Stable | — | -86,508.55 keV | 8,373.76 keV | — |
| Ce-138 | 0.251% | 4.4E+16 Y | Double electron capture (100%) | -87,565.87 keV | 8,377.04 keV | 3.29 × 10-40 eV |
| Ce-140 stable | 88.449% | Stable | — | -88,074.23 keV | 8,376.3 keV | — |
| Ce-142 | 11.114% | 5E+16 Y | Unknown | -84,532.9 keV | 8,347.07 keV | 2.89 × 10-40 eV |
Show all 38 isotopes
| Ce-121 | — | 1.1 s | Electron capture / beta-plus decay (100%), ECP (1%) | -52,690 keV | 8,132 keV | 4.15 × 10-16 eV |
| Ce-122 | — | — | Electron capture / beta-plus decay, ECP | -57,874 keV | 8,174 keV | — |
| Ce-123 | — | 3.8 s | Electron capture / beta-plus decay (100%), ECP (0%) | -60,286 keV | 8,193 keV | 1.20 × 10-16 eV |
| Ce-124 | — | 6 s | Electron capture / beta-plus decay (100%) | -64,916 keV | 8,229 keV | 7.60 × 10-17 eV |
| Ce-125 | — | 9.7 s | Electron capture / beta-plus decay (100%), Beta-plus, proton emission | -66,658 keV | 8,242 keV | 4.70 × 10-17 eV |
| Ce-126 | — | 51.0 s | Electron capture / beta-plus decay (100%) | -70,820.57 keV | 8,273.26 keV | 8.95 × 10-18 eV |
| Ce-127 | — | 34 s | Electron capture / beta-plus decay (100%) | -71,979.34 keV | 8,280.79 keV | 1.34 × 10-17 eV |
| Ce-128 | — | 3.93 m | Electron capture / beta-plus decay (100%) | -75,533.93 keV | 8,306.93 keV | 1.93 × 10-18 eV |
| Ce-129 | — | 3.5 m | Electron capture / beta-plus decay (100%) | -76,287.5 keV | 8,310.94 keV | 2.17 × 10-18 eV |
| Ce-130 | — | 22.9 m | Electron capture / beta-plus decay (100%) | -79,422.91 keV | 8,333.22 keV | 3.32 × 10-19 eV |
| Ce-131 | — | 10.3 m | Electron capture / beta-plus decay (100%), Beta-plus decay (11%) | -79,708.45 keV | 8,333.4 keV | 7.38 × 10-19 eV |
| Ce-132 | — | 3.51 h | Electron capture / beta-plus decay (100%) | -82,468.69 keV | 8,352.32 keV | 3.61 × 10-20 eV |
| Ce-133 | — | 97 m | Electron capture / beta-plus decay (100%) | -82,418.22 keV | 8,349.83 keV | 7.84 × 10-20 eV |
| Ce-134 | — | 3.16 d | Electron capture (100%) | -84,832.9 keV | 8,365.77 keV | 1.67 × 10-21 eV |
| Ce-135 | — | 17.7 h | Electron capture / beta-plus decay (100%) | -84,616.31 keV | 8,361.99 keV | 7.16 × 10-21 eV |
| Ce-137 | — | 9.0 h | Electron capture / beta-plus decay (100%) | -85,918.77 keV | 8,367.25 keV | 1.41 × 10-20 eV |
| Ce-139 | — | 137.63 d | Electron capture (100%) | -86,957.74 keV | 8,370.47 keV | 3.84 × 10-23 eV |
| Ce-141 | — | 32.504 d | Beta-minus decay (100%) | -85,431.06 keV | 8,355.4 keV | 1.62 × 10-22 eV |
| Ce-143 | — | 33.039 h | Beta-minus decay (100%) | -81,606.38 keV | 8,324.68 keV | 3.84 × 10-21 eV |
| Ce-144 | — | 284.91 d | Beta-minus decay (100%) | -80,431.94 keV | 8,314.76 keV | 1.85 × 10-23 eV |
| Ce-145 | — | 3.01 m | Beta-minus decay (100%) | -77,067.06 keV | 8,289.88 keV | 2.53 × 10-18 eV |
| Ce-146 | — | 13.49 m | Beta-minus decay (100%) | -75,625.87 keV | 8,278.51 keV | 5.64 × 10-19 eV |
| Ce-147 | — | 56.4 s | Beta-minus decay (100%) | -72,013.9 keV | 8,252.53 keV | 8.09 × 10-18 eV |
| Ce-148 | — | 56.8 s | Beta-minus decay (100%) | -70,398.42 keV | 8,240.39 keV | 8.03 × 10-18 eV |
| Ce-149 | — | 5.12 s | Beta-minus decay (100%) | -66,669.92 keV | 8,214.23 keV | 8.91 × 10-17 eV |
| Ce-150 | — | 4.0 s | Beta-minus decay (100%) | -64,846.86 keV | 8,201.12 keV | 1.14 × 10-16 eV |
| Ce-151 | — | 1.76 s | Beta-minus decay (100%) | -61,225.06 keV | 8,176.28 keV | 2.59 × 10-16 eV |
| Ce-152 | — | 1.4 s | Beta-minus decay (100%) | -58,980 keV | 8,161 keV | 3.26 × 10-16 eV |
| Ce-153 | — | 0.865 s | Beta-minus decay (100%), Beta-minus, neutron emission | -54,910 keV | 8,134 keV | 5.27 × 10-16 eV |
| Ce-154 | — | 0.722 s | Beta-minus decay (100%), Beta-minus, neutron emission | -52,220 keV | 8,116 keV | 6.32 × 10-16 eV |
| Ce-155 | — | 313 ms | Beta-minus decay (100%), Beta-minus, neutron emission | -47,780 keV | 8,087 keV | 1.46 × 10-15 eV |
| Ce-156 | — | 0.233 s | Beta-minus decay (100%), Beta-minus, neutron emission | -44,820 keV | 8,068 keV | 1.96 × 10-15 eV |
| Ce-157 | — | 0.18 s | Beta-minus decay (100%), Beta-minus, neutron emission | -39,930 keV | 8,037 keV | 2.53 × 10-15 eV |
| Ce-158 | — | 99 ms | Beta-minus decay (100%), Beta-minus, neutron emission | -36,540 keV | 8,015 keV | 4.61 × 10-15 eV |