lantanoidi

Lanthanoids are a series of 15 metallic chemical elements with atomic numbers from 57 to 71. They are located in the f-block of the periodic table, specifically in the sixth and seventh periods. The lanthanoids are named after lanthanum, the first element in the series, which is itself named after the Greek word "lanthanein," meaning "to lie hidden." This name reflects the difficulty in separating lanthanum from other rare earth elements.

The lanthanoids are often referred to as the rare earth metals, although they are not particularly rare in the Earth's crust. They are typically found in minerals such as monazite and bastnasite. The lanthanoids exhibit similar chemical properties due to the similar electron configurations of their atoms. They are all silvery-white metals that tarnish slowly in air and are relatively soft and malleable.

The lanthanoids are used in various applications, including as catalysts in the production of petroleum and synthetic rubber, in carbon arc lighting, and as components in magnets and electronic devices. They are also used in glassmaking to produce special optical glasses and in the production of high-strength alloys. Despite their usefulness, the lanthanoids are not as abundant as some other metals, and their extraction and purification can be complex and costly.