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Properties of s-,p-,d-,and f- Block elements September 4, 2008

Posted by jknepal in Inorganic.
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       The periodic table can be divided into four group of elements: 

      s-Block elements

       p-Block elements

     d-Block elements

     f-Block elements

            Salient features of the periodic table are:

  •  There are eighteen vertical columns called the groups
  • There are seven horizontal rows called periods.  The period number represents the principal quantum number of the valence shell of the elements present in it.
  • The periodic table is divided into four blocks of elements called s-, p-, d-, and  f- blocks.
  • In the Periodic Table discovered in 1869 by Dmitry I. Mendeleyev the elements are arranged to show their similarities and differences.  The noble gases are found in the 18th group at the right hand side of each period.
  • Elements found in groups (e.g. alkali, halogens) have a similar electronic configuration.
  • There is a progression from metals to non-metals across each period.

 

      Properties of s-Block elements (contain s-electrons in their valence shell)

     Except H all elements of s-Block elements are active metals.

    They have +1/ +2 oxidation state.

    They form basic oxides

   They impart characteristic colour to the flame

   Generally they form ionic salts with nonmetals.

   They have low ionization potentials.

   They have very small electron gain enthalpies.

   They are solids at room temperature (Cs is liquid at about at 35oC)

   Their hydroxides are basic in nature.

 

    Properties of p-Block elements: (contain p-electrons in their valence shell)

     Most of p-Block elements are non-metals.

    They have variable oxidation states.

    They form acidic oxides

    They impart no characteristic colour to the flame

     Generally they form covalent compounds. Halogens form salts with alkali metals

     They have high ionization potentials.

     They have very large electron gain enthalpies.

     They are solids/liquids/gases at room temperature (Br is liquid)

     The aqueous solutions their oxides are acidic in nature.

 

             Properties of d-Block elements: (contain d-electrons in their valence shell).

            These elements lie in between s-block and p-block elements. These elements   are called       transition elements as they show transitional properties between s and p-block elements. The general electronic configuration of d-block elements is (n-1)d1-10ns0-2.

       Most of the d-block elements are metals.

     Most of them exhibit variable oxidation states because of the presence of   partly filled d-orbitals.    (Except Sc, Zn, Cd etc.)

     Many of their compounds are coloured.

    They readily form complexes by acting as Lewis   acids.                                                                                                                                                                      They easily form complexes (coloured).                                                                                                           Most of them and their compounds show paramagnetic, ferromagnetic behaviour.                                                                                                                                                           They act as good catalysts.

 Properties of f-Block elements: (contain f-electrons in their valence shell).

 

Electronic configuration: ns2 (n-) d0-1(n-2) f1-14

 

 

 

        f – block elements are also called as inner transition elements. They are:                                        Lanthanides and actinides.

         Lanthanides. (58Ce-  71Lu )

  •  Actinides are the elements in which the last electron enters into 5f-orbital
  • All lanthanides closely resemble  lanthanum
  • Lanthanoids are chemically similar to each other
  • Except for cerium (III and IV) and europium (III and II), the lanthanides occur as trivalent cations in nature.                                                                                               Most lanthanides are widely used in lasers
  •  These elements deflect UV and Infrared electromagnetic radiation and are commonly used in the production of sunglass lenses. 
  •  The  ionic radii of the lanthanoids decrease through the period — the so-called    lanthanide contraction

         Actinides( 90Th– 103Lr)

·        All the actinides are radioactive

·        These are highly electro-positive ( show+3,+4,+5,+6  oxidation states)

·        These metals tarnish in air

·        They have number of isotopes.

·        They react with boiling water or dilute acids to give H2 gas.

·        These directly combine with non-metals.

 

Similarities between Lanthanides and Actinides:

 ·        Both lanthanides and Actinides show +3 oxidation states

·        Both are electropositive and very reactive

·        Both are paramagnetic

 

           Their geochemical behaviours are a function of ionic radius and  atomic number.                         This property results in variations in the abundances of  The lanthanide contraction is responsible for the great geochemical divide that splits the lanthanides into light and heavy-lanthanide enriched minerals.The divide is driven by the decrease in coordination number as the ionic radius shrinks, and is dramatically illustrated by the two anhydrous phosphate minerals, monazite (monoclinic) and xenotime (tetragonal). The geochemical divide has put more of the light lanthanides in the earths crust, but more of the heavies in the core.

 

 

 

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