Class 12 Chemistry D and F Block Elements Lanthanoid contraction:

Lanthanoid contraction:

  • As we move along the lanthanoid series, the atomic number gradually increases by one or we can say number of electrons and protons increases by one.
  • Addition of electrons to the same shell increases the effective nuclear charge.
  • Increase in atomic number also increases the number of electrons in the 4f orbital having poor shielding effect due to which the effective nuclear charge upon the outer electrons also increases.
  • Therefore the size of lanthanoids steadily decreases with the increase in the atomic number and phenomenon is called lanthanoid
  • As a result of lanthanoid contraction there is a similarity in the properties of second and third transition series.

 

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