Definition

1. Noun:
   • Any element of the lanthanide series: A lanthanoid is any one of the fifteen metallic chemical elements with atomic numbers 57 through 71 in the periodic table. These elements are also commonly known as lanthanides.

Usage

• The term is used primarily in scientific contexts, especially in chemistry, physics, and materials science, to refer to this specific series of elements.
• It is often used interchangeably with "lanthanide," though "lanthanoid" can be considered a more systematic term that aligns with the naming of other element groups (e.g., actinoid).

Examples

• Noun:
  • Lanthanum, the first lanthanoid, is used in camera lenses and studio lighting.
  • The chemist studied the magnetic properties of several lanthanoids.
  • These lanthanoid elements are known for their similar chemical behavior.

Advanced Usage

• "Lanthanoid contraction": A phenomenon in chemistry where the atomic radii of the elements decrease more than expected as the atomic number increases. This has significant effects on the properties of the elements that follow them in the periodic table.
  • The lanthanoid contraction explains why zirconium and hafnium have nearly identical chemical properties.

Variants and Related Words

• Lanthanide (n): The more common synonym for . The series is often called the lanthanide series.
• Rare-earth element (n): A broader category that includes the plus scandium and yttrium. Not all are technically "rare," but they are often grouped under this term.

Synonyms

• Lanthanide: The direct and most frequently used synonym.
• Rare-earth metal: A less precise synonym, as this term includes additional elements.

Notes on Meaning

• The series specifically includes the elements from lanthanum (atomic number 57) to lutetium (atomic number 71). While lanthanum itself gives the series its name, some classifications exclude it from the core group due to its electron configuration, but it is invariably included in the series definition.
• These elements are characterized by the filling of the 4f electron orbital.

Noun

1. any element of the lanthanide series (atomic numbers 57 through 71)