Cerium (Ce)
Cerium is element 58, a lanthanide in the lanthanide series (period 6). A neutral atom has 58 protons, 82 neutrons and 58 electrons, 2 of them valence electrons.
Lanthanide- Atomic number
- 58
- Atomic mass
- 140.12 u
- Valence electrons
- 2*
- Protons · neutrons
- 58 · 82
- Electrons per shell
- 2, 8, 18, 19, 9, 2
- At room temperature
- solid
Bohr model of cerium
The Bohr model draws cerium as a nucleus of 58 protons and 82 neutrons, with its 58 electrons on 6 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 19 in shell 4, 9 in shell 5, 2 in shell 6. Press Build the atom to watch the shells fill from the inside out. The outer ring (the P shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of cerium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹ 5d¹
Short form (noble gas notation): [Xe] 6s² 4f¹ 5d¹. The [Xe] stands for the electrons of xenon, the noble gas before it.
Cerium breaks the usual filling order. The Aufbau rule predicts 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f², but experiments show the configuration above. The energy levels of the subshells are so close here that a different arrangement wins.
How many valence electrons does cerium have?
Cerium has 2 valence electrons.
Cerium is a lanthanide, so its valence electrons are less clear-cut than for main-group elements. It has 2 electrons in its outermost shell (shell 6), and electrons in its inner f and d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 58 | equal to the atomic number |
|---|---|---|
| Electrons | 58 | equal to the protons in a neutral atom |
| Neutrons | 82 | mass number 140 − 58 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Cerium properties
| Symbol | Ce |
|---|---|
| Category | Lanthanide |
| Group · period · block | — · 6 · f |
| Atomic mass | 140.12 u |
| State at 25 °C | solid |
| Melting point | 1,071 K (798 °C, 1,470 °F) |
| Boiling point | 3,697 K (3,420 °C, 6,190 °F) |
| Density | 6.77 g/cm³ |
| Electronegativity (Pauling) | 1.12 |
| Atomic radius | 235 pm |
| First ionization energy | 5.539 eV |
| Electron affinity | 0.5 eV |
| Oxidation states | +4, +3 |
| Common ion charge | +4, +3 |
| Discovered | 1803 by Martin Heinrich Klaproth |
Where cerium sits on the periodic table
Lanthanides: Lanthanum, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium.
Questions about cerium
How many valence electrons does cerium have?
Cerium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does cerium have?
A neutral cerium atom has 58 protons and 58 electrons. Its most common form has about 82 neutrons (mass number 140 − 58 protons).
What is the electron configuration of cerium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹ 5d¹, written in short form as [Xe] 6s² 4f¹ 5d¹.
What does the Bohr model of cerium look like?
A nucleus of 58 protons and 82 neutrons, circled by 6 electron shells holding 2, 8, 18, 19, 9, 2 electrons.
What is the atomic number of cerium?
58. The atomic number is the number of protons in the nucleus, and it is what makes an atom cerium.