S- block Elements- ALKALI METALS

     We now move on to class 11 inorganic chemistry. The first

     chapter is s block elements. As mentioned before , NCERT is

     a must for all inorganic chapters. In these notes , i will be 

     covering the important points from ncert as well as some extra 

     points for jee advance.

     GROUP 1 ELEMENTS

     1. They are soft , conduct heat and electricity and have low 

         melting points.

      2. They possess weak metallic bonding. At room temperature,

         they exist in BCC structure. At low temperature , Li exists

         in hcp structure.

     3. Atomisation and Hydration energy decrease down the group.

     4. Except Li , other metals form alloys amongst themselves.

     5. Except Li , others show photoelectric effect.

     6. Flame colours :

  

         Li - Crimson

         Na- Yellow

         K  - lilac

         Rb - violet

         Cs - blue

     7. Rb and Cs react most vigorously with water because they sink

         in it. Reaction of lithium with water is very slow.

     8. K is less dense than Na.

     9. Only Li reacts directly with carbon and nitrogen. 

    10. Only Li reacts directly with oxygen to form oxides.

    
    NOTES:

   1. Lithium halides are the only ones which are not anhydrous. 
       They exist as LiX.3H2O.

   2. Sodium and other alkali metals dissolve in ammonia to form
       deep blue solutions. On long standing , they decompose 
       forming amides.

   3. Concentrated metal ammonia solutions have metallic bronze 
       colour and high electrical conductance.

   4. Lithium hydride is the most stable group 1 hydride.  This is
       due to similarity in the sizes of cation and anion.

   Extraction of Sodium :
   Method 1 : 

   1. Sodium is extracted by electrolysis of NaCl + CaCl2 solution.

   2. Calcium Chloride is added to lower melting point.

   3. Graphite anode , Steel cathode.

   
   Method 2 :

   Diaphragm Cell

   1. Diaphragm ( asbestos) prevents hydroxide ions from coming
       in contact with chloride ions. But Hydrogen and Chlorine still
       react. ( this is the disadvantage.)

   2. Cathode level is always less than anode. This ensures NaOH
       does not react with chlorine gas.

   3. The final solution always contains NaCl.

  
   Method 3 :

   Chloralkali process :

   http://www.eurochlor.org/the-chlorine-universe/how-is-chlorine-      produced/the-mercury-cell-process.aspx


 
   Compound of alkali metals :

   

  


   
   

     

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