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The d & f Block Elements — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryThe d & f Block Elements1 Mark
MCQ
Lanthanoid contraction occurs because:
  • A
    The $4f$ electrons, which are gradually added, create strong shielding effect.
  • B
    The $4f$ orbitals are greater in size than the 3d and 3f orbitals.
  • C
    The $5f$ orbitals strongly penetrate into the 4f orbitals.
  • ✓
    The poor shielding effect of $4f$ electrons is coupled with increased attraction between the nucleus and the added electrons.
✓

Answer

Correct option: D.
The poor shielding effect of $4f$ electrons is coupled with increased attraction between the nucleus and the added electrons.
Lanthanoid contraction occurs because the poor shielding effect of $4f$ electrons is coupled with increased attraction between the nucleus and the added electrons.
The atomic and ionic radii $(M^{3+}$ ions$)$ of Lanthanide elements decrease with increase in atomic number.

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