Class 12 Chemistry D and F Block Elements Comparison of Actinoids with Lanthanoids

General Characteristics and Comparison of Actinoids with Lanthanoids

(i) Electronic configuration

  • The general electronic configuration for actinoids is [Rn]86 5f1-14 6d0-1 7s2 and for lanthanoids is [Xe]54 4f0-14 5d0-1 6s2.

(ii) Atomic and lonic sizes

  • Like lanthanoids the ionic radii of actinoids gradually decrease across the series due to the poor screening effect of nuclear charge exerted by the f electrons.

(iii) Oxidation states

  • The lanthanoids exhibit +3 oxidation states. Some elements may exhibit + 2 and + 4 oxidation states due to extra stability of fully-filled and half-filled orbitals.
  • On the other hand Actinoids also exhibit + 3 oxidation state. They also exhibit varying oxidation states due to the comparable energies of 5f, 6d, and 7s.

(iv) Chemical reactivity

  • Earlier members of the lanthanide series are more reactive and are comparable to CSolution: They resemble Al with increasing atomic number.
  • Finely divided Actinoids are highly reactive metals and when added to boiling water gives a mixture of oxide and hydride.
  • At moderate temperatures Actinoids combine with most of the non-metallic elements.
  • Actinoids remain unaffected by the action of alkalies but gets slightly affected by nitric acid due to the formation of a protective oxide layer.

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