Question

Write the name of radioactive element in lanthanide series.

Hint:

Remember: Promethium is the "odd one out" in the lanthanide series because it is synthetic and radioactive, whereas all actinoids are radioactive.

Answer 1

Step 1: Understanding the Concept:
Lanthanides are the elements from atomic number 58 to 71. Most lanthanides are stable or have very long half-lives, except for one element.
Step 3: Detailed Explanation:
Promethium (\(Pm\)) with atomic number 61 is the only radioactive element in the Lanthanide series.
It does not occur naturally in the Earth's crust in significant amounts and is typically produced artificially.
Step 4: Final Answer:
The radioactive lanthanide is Promethium.