The lanthanide elements, also called the rare-earth elements, are a set of 15 metallic chemical elements with atomic numbers 57 to 71. They are: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

The lanthanide elements are all metals, and they are all relatively soft, silvery, and malleable. They are also all very reactive, and they readily form oxides, hydroxides, and salts.

The lanthanide elements are found in nature in a variety of minerals, including monazite, bastnäsite, and xenotime. They are also found in some ores, such as iron ore and copper ore.

The lanthanide elements are used in a variety of applications, including:

* In magnets: The lanthanide elements are used to make magnets that are stronger than traditional magnets.

* In lasers: The lanthanide elements are used to make lasers that produce a variety of colors.

* In phosphors: The lanthanide elements are used to make phosphors that glow in the dark.

* In catalysts: The lanthanide elements are used as catalysts for a variety of chemical reactions.

The lanthanide elements are an important part of the modern world, and they are used in a wide variety of applications.