Cerium (Ce)
Cerium (Ce) is a lanthanide with atomic number 58 and a standard atomic weight of 140.12. At room temperature it is a solid that melts at 799 °C and boils at 3,443 °C.
Cerium key facts
Cerium at a glance
Identity
| Symbol | Ce |
|---|---|
| Atomic number (Z) | 58 |
| Atomic weight | 140.12 ± 0.01 (CIAAW 2024) |
| Category | Lanthanide |
| Group | — (f-block: lanthanide series) |
| Period | 6 |
| Block | f-block |
| CAS number | 7440-45-1 |
Atomic properties
| Electron configuration | [Xe] 4f1 5d1 6s2 Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f1 5s2 5p6 5d1 6s2 |
|---|---|
| Electrons per shell | 2, 8, 18, 19, 9, 2 |
| Oxidation states | +3, +4 Less common: +1, +2 |
| Electronegativity (Pauling) | 1.12 |
| First ionisation energy | 5.539 eV (534.4 kJ/mol) 2nd: 10.956 eV · 3rd: 20.197 eV |
| Electron affinity | 0.65 eV |
| Atomic radius (empirical) | 185 pm |
| Covalent radius | 163 pm |
| Van der Waals radius | 242 pm |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Melting point | 799 °C · 1,470.2 °F · 1,072.15 K |
| Boiling point | 3,443 °C · 6,229.4 °F · 3,716.15 K |
| Density | 6.77 g/cm³ |
| Specific heat capacity | 0.192 J/(g·K) |
| Thermal conductivity | 11.3 W/(m·K) |
| Crystal structure | Face-centred cubic |
Isotopes & abundance
| Natural occurrence | Primordial |
|---|---|
| Radioactive | No |
| Natural isotopes (abundance) | 140Ce 88.449%, 142Ce 11.114%, 138Ce 0.251%, 136Ce 0.186% |
| Stable isotopes | 5 |
| Known isotopes | 41 |
| Abundance in Earth's crust | 66.5 mg/kg |
| Abundance in seawater | 0.0000012 mg/L |
Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.
Cerium electron configuration
Cerium has 58 electrons. Written in short form, its ground-state configuration is [Xe] 4f1 5d1 6s2 — the electrons of the noble gas xenon, plus 4f1 5d1 6s2.Written out in full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f1 5s2 5p6 5d1 6s2.
An exception to the filling rule. The simple aufbau (Madelung) order predicts 4f2, 5d0, but cerium actually has 4f1, 5d1. Half-filled and filled subshells, and the close energies of the outer orbitals, make this arrangement more stable.
Discovery and name
1803 — Jöns Jacob Berzelius and Wilhelm Hisinger; independently Martin Heinrich Klaproth · Sweden / Germany.
The dwarf planet Ceres, discovered in 1801.
Known for
The most abundant rare-earth element. Cerium oxide polishes glass and is used in catalytic converters; ferrocerium makes lighter flints.
Isotopes of cerium
Naturally occurring cerium is a mix of 4 isotopes. Each has 58 protons; they differ in the number of neutrons:
| Isotope | Protons | Neutrons | Natural abundance | Stability |
|---|---|---|---|---|
| 140Ce | 58 | 82 | 88.449% | stable |
| 142Ce | 58 | 84 | 11.114% | stable |
| 138Ce | 58 | 80 | 0.251% | stable |
| 136Ce | 58 | 78 | 0.186% | stable |
41 isotopes of cerium are known in our data set (half-lives as published in nuclear data tables).
Cerium and its neighbours in the lanthanide series
Neighbouring elements in the same f-block series:
| Element | Z | Atomic weight | Melting point | Boiling point | Density | Electronegativity |
|---|---|---|---|---|---|---|
| Lanthanum | 57 | 138.91 | 920 °C | 3,464 °C | 6.15 g/cm³ | 1.1 |
| Cerium | 58 | 140.12 | 799 °C | 3,443 °C | 6.77 g/cm³ | 1.12 |
| Praseodymium | 59 | 140.91 | 931 °C | 3,520 °C | 6.773 g/cm³ | 1.13 |
| Neodymium | 60 | 144.24 | 1,016 °C | 3,074 °C | 7.01 g/cm³ | 1.14 |
| Promethium | 61 | [145] | 1,042 °C | 3,000 °C | 7.26 g/cm³ | 1.13 |