Which of the following elements is classified as a lanthanoid group element?

Correct option is A

Correct Answer: (a) Cerium
Explanation:

• Cerium (Ce) belongs to the lanthanoid series, which includes elements with atomic numbers 57–71.

• Lanthanoids are also known as rare earth elements and show similar chemical properties due to the filling of the 4f-orbitals.
Information Booster:

• Lanthanoid series starts with Lanthanum (57) and ends with Lutetium (71).

• These elements exhibit +3 oxidation state commonly.

• Used in alloys, magnets, catalysts, and electronics.

• Cerium is the most abundant lanthanoid and is used in catalytic converters.
Additional Knowledge:

• (b) Scandium → A transition metal, belongs to group 3, not a lanthanoid.

• (c) Yttrium → Though chemically similar to lanthanoids, it is classified as a transition metal.

• (d) Actinium → Belongs to the actinoid series, not the lanthanoids.