Cerium
[Xe] 4f¹ 5d¹ 6s² · 2 · 8 · 18 · 19 · 9 · 2
The most abundant lanthanide — commoner in the crust than copper. Cerium is the only lanthanide with a stable +4 state, and the whole of automotive catalytic chemistry runs on its switch between +3 and +4.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 58
- Atomic mass
- 140.116 а.е.м.
- Electron configuration
- [Xe] 4f¹ 5d¹ 6s²
- Electrons per shell
- 2 · 8 · 18 · 19 · 9 · 2
- Block
- f-block
- Group
- no data
- Period
- 6
- Electronegativity (Pauling)
- 1.12
- Electronegativity (Allen)
- 1.09
- Atomic radius
- 235 pm
- Covalent radius
- 204 pm
- Van der Waals radius
- 235 pm
- Ionisation energy 1
- 534.4 kJ/mol
- Ionisation energy 2
- 1 050 kJ/mol
- Ionisation energy 3
- 1 949 kJ/mol
- Ionisation energy 4
- 3 547 kJ/mol
- Ionisation energy 5
- 6 325 kJ/mol
- Electron affinity
- 50 kJ/mol
- Common oxidation states
- +3, +4
- Oxidation states
- +1, +2, +3, +4
Physical properties
- State at 25 °C
- solid
- Density
- 6.77 g/cm³
- Melting point
- 1 068 K · 794.9 °C
- Boiling point
- 3 716 K · 3 442.9 °C
- Speed of sound
- 2 100 m/s
Thermal properties
- Heat of fusion
- 5.46 kJ/mol
- Heat of vaporisation
- 398 kJ/mol
- Specific heat capacity
- 0.192 J/(g·K)
- Thermal conductivity
- 11.3 W/(m·K)
Mechanical properties
- Young's modulus
- 33.6 GPa
- Shear modulus
- 13.5 GPa
- Bulk modulus
- 21.5 GPa
- Poisson ratio
- 0.24
- Mohs hardness
- 2.5
- Brinell hardness
- 412 MPa
Electrical and magnetic properties
- Electrical resistivity
- 828 nΩ·m
- Magnetic ordering
- paramagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- 0.022 K
Crystal structure
- Crystal structure
- face-centred cubic (fcc)
- Lattice constants
- a = 516.1 pm
Abundance
- In the crust
- 66.5 mg/kg
- In the ocean
- 1.2·10⁻⁶ mg/L
- In the universe
- 1 mg/kg
- In the human body
- no data
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 136Ce | 0.185 % | stable | — |
| 138Ce | 0.251 % | stable | — |
| 140Ce | 88.45 % | stable | — |
| 142Ce | 11.114 % | stable | — |
Four natural isotopes. Cerium-144, half-life 285 days, is a fission product once considered as a source for sterile neutrino searches.
Discovery
- Year of discovery
- 1803
- Discovered by
- Berzelius, Hisinger and Klaproth
- Where
- Sweden and Germany
- Origin of the name
- after the dwarf planet Ceres, discovered two years earlier
History
Berzelius and Hisinger in Sweden and Klaproth in Germany discovered cerium independently in 1803. It was named after the dwarf planet Ceres, found two years earlier.
Where it occurs
66.5 mg/kg of the crust — the twenty-fifth most abundant element, ahead of tin and lead. The main minerals are bastnäsite and monazite.
How it is produced
From rare-earth concentrates; cerium separates more easily than the rest precisely because of that stable +4 state.
Role in living things
No biological role. Cerium salts served as antiemetics in the nineteenth century and are used in burn treatment today.
Safety
Of low toxicity. Powdered cerium metal is pyrophoric and ignites on friction — which is precisely how a lighter flint works.
Uses
- Ceria in automotive catalysts: it stores and releases oxygen, buffering swings in mixture composition
- Polishing powders for glass and optics — the finest finishing abrasive there is
- Mischmetal in lighter flints and pyrotechnic alloys
- Ultraviolet filters in glass
- Scintillators for radiation detectors
Curiosities
- Cerium is named after Ceres, the dwarf planet found in 1801.
- A lighter flint is not flint but a cerium-iron alloy: it sparks under friction because cerium is pyrophoric.
- There is more cerium in the crust than copper, tin, lead or cobalt.
- Ceria can give up oxygen from its lattice and take it back without falling apart — a rare property indeed.