VESPR Theory - Valence Shell Electron Pair Repultion Theory
- it enables us to determine the shape of individual molecule repulsion between electron pairs.
Class # of bonding pairs. # of lone pairs. Arrangement. Molecular Geometry
AB2 2 0. linear. linear
AB3. 3. 0. trigonal planar. trigonal planar
AB4. 4. 0. tetrahedral. tetrahedral
AB5. 5. 0. trigonal bipyramidal. trigonal bipyramidal
AB6. 6. 0. octahedral. octahedral
Linear - the two bonding pairs moved in opposite directions, making an angle of 180 degrees with each other.
No. of atoms bonded : 2
No. of lone pairs : 0
- non- planar
Ex. BeF2
Trigonal Planar -120 degrees.
example : BF3
HCN - central atom - greater no. pf unpaired electrons
Substituent atoms - Bond with central atoms
Tetrahedral - 109.5 degrees
Trigonal Bipyramidal - 90 , 120, 180 degrees
Example : PCl5
Octahedral - 90 and 180 degrees
Example : SF6
Exception to the octet rule :
Incomplete Octet : Be, B, Al, Ga, Ge, In, Sn
Expanded Octet : P , S , Cl , Kr
