Properties and Overview of Lanthanum

Overview:

Lanthanum (La) with the chemical symbol La and atomic number 57, is the first element in the lanthanide series, a group of 15 metallic elements known for their similar properties. Lanthanum is a silvery-white metal that is soft, malleable, and ductile, making it relatively easy to work with. It was discovered in 1839 by the Swedish chemist Carl Gustaf Mosander, who separated it from cerium, another rare earth element. The name "lanthanum" is derived from the Greek word "lanthanein," meaning "to lie hidden," reflecting the element's elusive discovery. Physically, lanthanum is notable for its softness and relatively low density among the lanthanides, with a density of about 6.15g/cm³. It has a melting point of 920°C and a boiling point of 3,464°C. Lanthanum has a hexagonal crystal structure at room temperature but transitions to a face-centered cubic structure at higher temperatures. The metal is highly reactive, especially when freshly cut, as it quickly tarnishes in the air due to the formation of an oxide layer on its surface.
Chemically, lanthanum is quite reactive, more so than many of the other lanthanides. It readily oxidizes in air, forming lanthanum oxide (La₂O₃), which is a white, powdery substance. Lanthanum reacts slowly with water, producing lanthanum hydroxide and hydrogen gas, and it dissolves in most acids, releasing hydrogen and forming corresponding lanthanum salts. Lanthanum primarily exhibits a +3 oxidation state in its compounds, a characteristic it shares with other lanthanides. Lanthanum compounds, such as lanthanum chloride (LaCl₃) and lanthanum nitrate (La(NO₃)₃), are typically white or colorless and are often used in various chemical processes.
Regarding safety, lanthanum metal is not considered highly toxic, but care should be taken when handling it. The primary concerns arise from its compounds, particularly in powdered form, as they irritate the skin, eyes, and respiratory system. Inhalation of lanthanum compounds can lead to respiratory issues, so adequate ventilation and protective equipment are recommended when working with these materials. There is limited information on the long-term health effects of lanthanum exposure, but as with many metals, it is prudent to minimize unnecessary exposure.

Production:

Lanthanum is typically produced by extracting it from rare earth minerals, such as monazite and bastnäsite, where it is found in significant quantities. The extraction process usually involves crushing the mineral and chemical treatment to separate the various rare earth elements. Lanthanum is often separated from other lanthanides through ion exchange and solvent extraction techniques. After separation, lanthanum is converted into its oxide or other compounds, which can be reduced to metallic lanthanum through electrolysis or chemical reduction.

Applications:

Due to its unique properties, lanthanum has a wide range of applications across various industries. One of the most significant uses of lanthanum is in producing catalysts. Lanthanum oxide is a critical component in fluid catalytic cracking (FCC) catalysts used in oil refineries to convert crude oil into gasoline and other products. The inclusion of lanthanum improves the efficiency and durability of these catalysts.
In the electronics industry, lanthanum is used to produce phosphors for color television and LED displays. Lanthanum-doped glass is used in camera lenses and other optical instruments, improving the refractive index and reducing optical aberrations. Additionally, lanthanum is used to manufacture high-refractive-index glass, which is essential for high-quality lenses and optical fibers.
Lanthanum is also a critical component in the production of rechargeable nickel-metal hydride (NiMH) batteries, which are used in hybrid vehicles and portable electronics. Adding lanthanum to the battery's electrodes increases the battery's efficiency and longevity.
In medicine, lanthanum carbonate is used as a phosphate binder in patients with chronic kidney disease. By binding to phosphate in the digestive tract, lanthanum carbonate helps reduce phosphate levels in the blood, which is crucial for managing kidney disease.
Other applications of lanthanum include its use in hydrogen storage materials, in metal alloys to improve strength and corrosion resistance, and as a component in lighter flints due to its pyrophoric nature (the ability to ignite spontaneously when scratched or struck). Lanthanum is also used in the production of specialty alloys and in the ceramics industry to improve certain materials' durability and thermal stability.

Summary:

Lanthanum is a versatile and reactive rare earth metal with various industrial and medical applications. Its physical and chemical properties make it suitable for catalysts, electronics, optical devices, batteries, and other technologies. While generally safe to handle, precautions should be taken to prevent respiratory and skin irritation when working with lanthanum compounds, particularly in powdered form. The production of lanthanum involves complex extraction and separation processes, reflecting its importance in modern industry and technology.

See a comprehensive list of atomic, electrical, mechanical, physical and thermal properties for lanthanum below: