La#58 / 118Pr

58Ce140.12

Lanthanides (Rare Earths)solid at STPF-block

Cerium

Group: f-block•Period: 6•Standard Atomic Weight: 140.12 u

Open Full Periodic Table View Bohr Model

Why is Cerium in this position?

Understanding the scientific rationale behind Cerium's position in the periodic table:

Group Assignment

Group Lanthanide / Actinide

Lanthanide series element filling the 4f subshell.

Period Assignment

Period 6

Belongs to Period 6 because its outermost electrons occupy n=6.

Orbital Block

F-block

Belongs to the f-block because electrons occupy 4f orbitals.

Chemical Category

Lanthanides (Rare Earths)

Classified as a lanthanide rare earth metal with unique +4 and +3 redox chemistry.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 18, 19, 9, 2]

Bohr Atomic Shell Model(2, 8, 18, 19, 9, 2)

Hover or tap any shell orbit ring to inspect electron counts and 2n² capacities.

58 Protons (p⁺)82 Neutrons (n⁰)

Educational Note: This Niels Bohr planetary model visually illustrates principal quantum energy shells ($n=1, 2, 3\dots$) and electron counts. In modern quantum mechanics (Schrödinger model), electrons do not orbit in fixed circular planetary tracks, but exist as 3D probability clouds (orbitals: $s, p, d, f$) governed by the Heisenberg uncertainty principle.

Electron Shell Filling Breakdown

Shell K (n=1):2 / 2 electrons (100%)

Shell L (n=2):8 / 8 electrons (100%)

Shell M (n=3):18 / 18 electrons (100%)

Shell N (n=4):19 / 32 electrons (59%)

Shell O (n=5):9 / 50 electrons (18%)

Shell P (n=6):2 / 72 electrons (3%)

Aufbau Electron Configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹ 5s² 5p⁶ 5d¹ 6s²

Neutral ground state configuration. Valence electrons: 4.

Atomic & Quantum Properties

Electronegativity (Pauling)1.12 Pauling

1st Ionization Energy534.4 kJ/mol

Electron Affinity-50 kJ/mol

Atomic Radius (empirical)185 pm

Common Oxidation States+3, +4

Crystal StructureFCC

Physical & Thermal Properties

Density at STP6.77 g/cm³

Melting Point798 °C (1071 K)

Boiling Point3443 °C (3716 K)

Magnetic OrderingParamagnetic

Discovery Year1803

Discovered ByMartin Heinrich Klaproth, Jöns Jacob Berzelius & Wilhelm Hisinger

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses

Cerium(IV) oxide (CeO₂) high-precision chemical-mechanical polishing (CMP) for silicon wafers and optical glass
Automotive three-way catalytic converters as an oxygen storage buffer (CeO₂ ⇄ Ce₂O₃)
Mischmetal flint alloy in cigarette lighters and spark igniters
Self-cleaning oven catalytic wall coatings

Occurrence in Nature

The most abundant rare earth, extracted commercially from bastnäsite and monazite ores.

Etymology & Name Origin

Named after the dwarf planet Ceres, which had been discovered in 1801

Important Chemical Compounds

CeO₂ (Ceria / Cerium dioxide)

Ce(SO₄)₂ (Cerium(IV) sulfate / Analytical oxidizer)

CeCl₃ (Cerium trichloride)

Interesting Chemical Facts

• Cerium oxide (CeO₂) is so versatile in catalytic converters because it effortlessly switches between Ce⁴⁺ and Ce³⁺, acting as an oxygen sponge.
• Cerium iron alloys (ferrocerium / 'flint') produce bright 3,000 °C sparks when struck against steel, used in all campfire firesteels and lighters.
• Despite being labeled a 'rare earth', cerium is the 25th most abundant element in Earth's crust (66 ppm).

Safety & Handling Note

Cerium shavings and dust are pyrophoric and ignite easily; mild biological toxicity.