Lanthanum
Definition and meaning of Lanthanum in chemistry.
Lanthanum is a soft, ductile, silvery-white rare-earth metal with the symbol La and atomic number 57. It is the defining prototype element of the lanthanide series and tarnishes very rapidly when exposed to ambient air.
In more detail
Positioned in group 3 of the periodic table, lanthanum is the very first element of the closely related lanthanide series, a unique group of elements that share nearly identical physical and chemical properties. It is highly chemically reactive, oxidizing swiftly in the presence of air to form a crumbly white powder of lanthanum(III) oxide (La2O3) and reacting vigorously with hot water to form basic lanthanum hydroxide (La(OH)3). Lanthanum is predominantly found in complex rare-earth minerals such as cerite, monazite, and bastnasite, typically existing in tight chemical combination with cerium and other lanthanides. It exhibits a highly stable +3 oxidation state in almost all of its isolated compounds. Because of its strongly electropositive nature and excellent ability to form robust bonds with nonmetals, lanthanum is extensively utilized in modern catalytic applications and acts as a powerful alloying agent to significantly improve the physical properties of other industrial metals.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | La |
| Atomic number | 57 |
| Atomic mass | 138.91 u |
| Category | Lanthanide |
| State at room temperature | Solid |
| Melting point | 920 °C |
| Boiling point | 3464 °C |
| Year discovered | 1839 |
Lanthanum is a major structural component in rechargeable nickel-metal hydride (NiMH) batteries, which are widely deployed in modern hybrid electric vehicles and countless portable consumer electronics due to their high energy density and reliability.
Frequently asked questions
Is lanthanum truly considered a rare earth element by modern geologists?
Yes, lanthanum is officially classified as a rare earth element, though despite the historical name, it is actually quite abundant in the Earth's upper crust, being significantly more common than familiar elements like lead or silver.
What is mischmetal and what is its primary real-world application?
Mischmetal is a specialized, highly pyrophoric alloy of rare-earth elements containing a significant percentage of lanthanum and cerium, which is universally used to manufacture the standard sparking flint mechanism found in modern pocket lighters.