Alkali Metal Notes

       ALKALI METAL

·       Alkali metals

   The metal of group IA like Li, Na, K, Rb, Cs and Fr dissolve in water to give metal hydroxide. They are ionized to give hydroxide ion and act a strong alkali. Therefore, group IA metal are called as alkali metal. The last element Fr is radioactive.

       2Na + 2H₂O ----------» 2NaOH + H₂

          NaOH       ----------»Na⁺ + OH^-

     2K + 2H₂O    ----------» 2KOH + H₂

          KOH        ----------» K⁺ + OH^-

 

·       Characteristics of Alkali metal

1)   Electronic configuration

        Alkali meta has 1 electron in valence shell and has electronic configuration ns¹ where n represents number of shell.

Example: Li ----------»1s²,2s¹

               Na----------»1s²,2s²2p⁶,3s¹

               K----------»1s²,2s²2p⁶,3s²3p⁶,4s¹

2)   Valency and oxidation state

     Due to the presence of only one electron in the valence shell, it shows valency +1 and +1 oxidation states.

    Na----------»Na⁺ + e^-

3)  Atomic and ionic size

        Alkali metals have greater size in period and the size goes on increasing in a group.

4) Boiling point and melting point

     Due to greater size of alkali metal, there is weak metallic bonding due to which melting point and boiling point is low.

5)   Reactivity

             Due to greater size of alkali metal, the valence electron can be removed easily. So that reactivity is high in period and it goes on increasing in group. 

     6) Flame colouration

           Due to greater size of alkali metal, the valence electron are weakly attracted by the nucleus. When alkali metal are heated in oxidizing flame, the valence electron absorb heat energy and excited to higher energy level. But at higher energy  level, the electron are unstable so immediately, it returns back to the ground state on doing. So, it emits  the absorbed heat in the form of radiation giving different colours to the flame.

  Example: Li----------»Crimson color

                  Na----------»Golden yellow

                  K ----------» Purple

                  Rb----------»violet

·       Na cannot be extracted from NaCl by using Carbon reduction process

1)      Na itself is a strong reducing agents. So, it’s oxide and halide cannot be reduce by using Carbon

2)      Na show greater affinity toward oxygen than that of Carbon

3)       Carbon reduction process take place at high temperature at high temperature. Na combine with Carbon to form carbide