Which of the following elements is a member of the actinoid series?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. Thorium.
- Thorium is actually a member of the actinide series, not the actinoid series. Actinide series, also known as actinides, refers to a group of chemical elements in the periodic table that are part of the f-block.
- These elements are characterized by having partially filled 5f electron orbitals. Thorium (symbol: Th, atomic number: 90) is indeed one of the actinide elements.