History and Discovery
Lanthanum is a chemical element with the symbol La and atomic number 57. It is one of the 15 lanthanides, a series of elements with atomic numbers ranging from 57 to 71. The discovery of lanthanum dates back to 1839 when Swedish chemist Carl Gustaf Mosander isolated it from cerium (Ce) carbonate. Initially, Mosander named it "lanthana" after the Greek word "lanthanein," meaning "to lie hidden," as it was difficult to distinguish from other rare earth elements. Later, the name was changed to lanthanum.
Physical and Chemical Properties
Lanthanum is a soft, silvery-white, malleable, and ductile metal with a melting point of 920°C and a boiling point of 3464°C. It is highly reactive and tends to lose three electrons to form a +3 ion. Lanthanum is a relatively large element with an atomic radius of 187.6 pm and a density of 6.145 g/cm³. It is also a good conductor of electricity and heat. Lanthanum has several allotropic forms, including a hexagonal and a cubic form.
Compounds and Applications
Lanthanum forms various compounds, including oxides, halides, and carbonates. The most common oxide of lanthanum is La2O3, which is used as a catalyst in petroleum refining. Lanthanum halides, such as LaF3, are used in the manufacture of fluorescent lamps and in the production of glass. Lanthanum carbonate (La2(CO3)3) is used in the production of ceramics and in the manufacture of glass.
Lanthanum has several applications due to its unique properties. It is used in the production of high-performance glasses, such as those used in telescopes and other optical instruments. Lanthanum-based catalysts are used in the petroleum industry to improve the yield of petroleum products. Lanthanum is also used in the production of fuel cells and in the manufacture of phosphors for use in lighting and display devices.
Occurrence and Extraction
Lanthanum is a relatively rare element, making up about 0.001 ppm (parts per million) of the Earth's crust. It is typically found in association with other rare earth elements, such as cerium and neodymium. The main sources of lanthanum are monazite, a phosphate mineral containing rare earth elements, and bastnäsite, a carbonate mineral containing rare earth elements.
Lanthanum is extracted from these minerals through a complex process involving several steps. The minerals are first crushed and concentrated through a process called flotation. The resulting concentrate is then roasted to produce a mixture of oxides, which is then leached with a solvent to produce a solution of lanthanum ions. The lanthanum ions are then precipitated out of solution as a carbonate or oxalate, which is then converted to the metal through electrolysis or reduction with a metal such as magnesium.
Nuclear Applications and Toxicity
Lanthanum has several nuclear applications due to its unique properties. It is used as a neutron absorber in nuclear reactors to slow down the reaction and prevent overheating. Lanthanum is also used in the production of nuclear fuels, such as uranium-235, which is used in nuclear reactors.
Lanthanum is generally considered to be non-toxic, but it can be a fire hazard due to its high reactivity. It can also release toxic fumes when heated in air. The inhalation of lanthanum dust can cause lung damage and other respiratory problems.
References
This article has been written based on the following sources:
- Haynes, W. M. (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press.
- Lide, D. R. (2007). CRC Handbook of Chemistry and Physics (88th ed.). CRC Press.
- Greenwood, N. N., & Earnshaw, A. (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann.
- Cotton, F. A., & Wilkinson, G. (1988). Advanced Inorganic Chemistry (5th ed.). John Wiley & Sons.
- Emsley, J. (2011). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press.