Category: Lanthanide
Atomic Number: 57
Period: 6 | Group: N/A
Block: f-block
The first lanthanide and the element that hid inside cerium for 36 years before anyone noticed.
| Property | Value |
|---|---|
| Phase at STP | Solid |
| Density | N/A |
| Melting Point | 1193.00 K (919.85 °C) |
| Boiling Point | 3737.00 K (3463.85 °C) |
| Heat Capacity | N/A |
| Property | Value |
|---|---|
| Atomic Mass | 138.9055 u |
| Electronegativity (Pauling) | N/A |
| Oxidation States | +2, +3 |
| Electron Configuration |
| Discovered By | Unknown |
|---|---|
| Discovery Year | 1839 |
| Named After | Greek lanthanein, "to lie hidden" |
The Discovery Saga
1839 - The First Clue
Carl Gustav Mosander , a Swedish chemist and student of the great Jöns Jakob Berzelius, was studying cerium nitrate when he noticed something peculiar. The supposedly pure cerium exhibited properties that didn't quite match what was expected.
The Separation Triumph
Through meticulous fractional crystallization - a painstaking process of repeatedly dissolving and recrystallizing compounds - Mosander managed to separate what he thought was pure cerium into two distinct substances .
Naming the Element
Mosander named the new element "lanthanum" from the Greek word "lanthanein," meaning "to lie hidden" . This was very prophetic - lanthanum had indeed been hiding in cerium samples for decades!
Historical Context
Mosander's discovery came during the golden age of elemental discovery. In 1843 he also discovered terbium and erbium . His systematic approach to separating rare earth elements laid the groundwork for understanding the entire lanthanide series.
Scientific Impact
Mosander's discovery of lanthanum was important because it proved that even "well-known" elements could harbor hidden secrets. This discovery sparked a 70-year quest to separate and identify all the rare earth elements, fundamentally changing our understanding of atomic structure and periodicity.
Mosander's Legacy
Carl Mosander discovered three rare earth elements, lanthanum, erbium and terbium, and the mixture didymium. His methodical approach to rare earth separation influenced generations of chemists and helped make Sweden a leading center of early elemental chemistry.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| La-138 | 81 | 0.08881% | 1.03 × 10¹¹ yrs | ε/β⁺ (65.5%), β⁻ (34.5%) |
| La-139 | 82 | 99.91119% | Stable | - |
Data: IAEA Nuclear Data Section, LiveChart of Nuclides, ground-state evaluations, retrieved October 10, 2026. Abundance is the share of atoms in the natural element; a dash means the isotope has no standard natural abundance.
Advanced Industrial Applications
Lanthanum is the gateway element to the lanthanide series and plays crucial roles in modern technology. As a catalyst extraordinaire , lanthanum compounds are essential in petroleum refining, where they help crack heavy crude oil into gasoline and diesel fuel that powers our world.
Camera Lenses
High-end camera lenses contain lanthanum glass - up to 50% by weight! This special glass has a very low dispersion, meaning it bends different colors of light by almost the same amount, eliminating the rainbow fringes (chromatic aberration) that plague cheaper lenses. When you see those crystal-clear, professional photographs, lanthanum is working behind the scenes.
Battery Technology
Nickel-metal hydride (NiMH) batteries - found in hybrid cars like the Toyota Prius - rely on lanthanum-based alloys to store hydrogen. A typical hybrid car battery contains about 10-15 kg of lanthanum , making it one of the largest industrial uses of this rare earth element.
Lighter Flints & Spark Generation
The "flint" in cigarette lighters is actually a mischmetal alloy containing 25-50% lanthanum. When struck, lanthanum creates the bright sparks that ignite the fuel. This same technology is used in welding electrodes and theatrical pyrotechnics.
Advanced Materials
Hydrogen storage materials for fuel cell research
Superconducting materials when combined with copper and oxygen
Phosphor materials for energy-efficient lighting
Ceramic capacitors for electronic devices
| Earth's Crust | N/A |
|---|---|
| Universe | N/A |