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NEET Chemistry QUESTION #7389
Question 1
Lanthanoids are best described as:
  • 14 elements in the seventh period (Z = 58 to 71) filling the 4f sub-level
  • 14 elements in the sixth period (Z = 90 to 103) filling the 4f sub-level
  • 14 elements in the seventh period (Z = 90 to 103) filling the 5f sub-level
  • 14 elements in the sixth period (Z = 58 to 71) filling the 4f sub-level✔️
Correct Answer Explanation
Lanthanoids:
  • Atomic numbers: 58 to 71 (Ce to Lu)
  • Period: Sixth (belong to period 6)
  • Sub-level being filled: 4f
  • Total: 14 elements
They are placed in the f-block of the periodic table. Note: Actinoids (Z = 90 to 103) are in the 7th period and fill the 5f sublevel — a common source of confusion.