On Wednesday, June 15, 2005 at 5:14:24 PM UTC+5:30, josef muller wrote:   
   > hello,   
   > i have read that the difference in the shape of molecule of NH3 and   
   > PH3 stems from different hybridization. can anybody explain me this?   
   > electron configurations of N and P are rather similar (2s2 2p3 and 3s2   
   > 3p3). why they are different in shape? is VSEPRT helpful in this case?   
   >   
   > thank you.   
      
   See...   
   Its the case of Drago's rule.   
   It is an empirical rule used to explain the bond angles of group 15 and 16.   
   According to this, when the following conditions are satisfied, the energy   
   difference between the participating orbitals will be very high and thus no   
   mixing or hybridization takes place. The conditions are :   
   1) the central atom must be of 3rd, 4th, 5th period,etc.   
   2) The central atom should have atleast 1 lone pair   
   3) No. of lone pair + bond pair = 4   
   4) The electronegativity of the surrounding atom must be less than or equal to   
   2.5 .   
      
   So, apart from NH3, the hydrides of the other group members have no   
   hybridisation, but would have triagonal pyramidal shape ...But NH3 has sp3   
   hybridisation and triagonal pyrimadial shape...   
      
   Hope you understood :   
      
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