Correct Answer - Option 1 : Actinide series
Explanation:
In the periodic table, Actinoid element or the actinide element, any of a series of 15 consecutive chemical elements from actinium to lawrencium (atomic numbers 89–103).
- As a group, Actinoid elements are significant largely because of their property of being radioactive.
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Curium (Cm), a synthetic chemical element having atomic number 96 comes under the Actinoid series of the periodic table.
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Actinoid elements are actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium and lawrencium.
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58-71 atomic numbers belong to the first series of the f-block i.e., the lanthanides.
- Lanthanides start from Lanthanum and the last lanthanide is Lutetium.
- But, similar to Actinium, Lanthanum (atomic no. 57) is not included in the f-block and belongs to the group 3.
- Hence, the f-block lanthanides are from atomic number 58-71.
- The Lanthanide series include: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.