Which of the following elements is calssified as an actinoid group element?

Correct option is A

Correct Answer: (a) Thorium

Explanation:

• Actinoids (Actinides) are elements with atomic numbers 89 to 103 (from Actinium to Lawrencium).
• Thorium (Th, Z = 90) belongs to this group, known for being radioactive and mostly found in the f-block of the periodic table.
• Actinoids include elements like Uranium, Plutonium, and Thorium, used in nuclear energy.

Information Booster:

• Actinoids show variable oxidation states and are mostly radioactive.
• Thorium is used as a nuclear fuel in reactors.
• Actinoids are part of the 7th period in the periodic table.
• The term “rare earth elements” generally refers to lanthanides, not actinides.
• Lanthanides + Actinides are collectively called f-block elements.

Additional Knowledge:

• Ytterbium (Z=70): A lanthanoid, not an actinoid.
• Lanthanum (Z=57): First element of the lanthanoid series.
• Cerium (Z=58): Also a lanthanoid, used in alloys and polishing powders.