Question:
Which of the following lanthanoids is radioactive?
Which of the following lanthanoids is radioactive?
Show Hint
Promethium (Pm) is the only radioactive lanthanoid.
Updated On: Oct 1, 2026
- Tm
- Dy
- Eu
- Pm
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Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Among the 15 lanthanoids (La to Lu), all are stable or nearly stable except one element which has no stable isotope.
Step 2: Recall the fact:
Promethium (Pm, atomic number 61) is radioactive. It does not occur in significant amounts in nature.
Step 3: Why the other options are wrong.
Thulium (Tm), dysprosium (Dy) and europium (Eu) all have stable isotopes and are not radioactive.
Final Answer:
Promethium is the radioactive lanthanoid. \[ \boxed{\text{(D) }\text{Pm}} \]
Among the 15 lanthanoids (La to Lu), all are stable or nearly stable except one element which has no stable isotope.
Step 2: Recall the fact:
Promethium (Pm, atomic number 61) is radioactive. It does not occur in significant amounts in nature.
Step 3: Why the other options are wrong.
Thulium (Tm), dysprosium (Dy) and europium (Eu) all have stable isotopes and are not radioactive.
Final Answer:
Promethium is the radioactive lanthanoid. \[ \boxed{\text{(D) }\text{Pm}} \]
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