Chemistry help!!!Watch this thread
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2 Regions of electron density: linear, 180
3 regions: trigonal planar, 120
4 regions: tetrahedral, 109.5
5 regions: trigonal bipyramidal, 90 and 120
6 regions: octahedral, 90
The above shapes occur when there are only bonded pairs. Lone pair-lone pair repulsion is greater than bonding pair-lone pair and bonding pair-bonding pair repulsion, so each lone pair squeezes the bond angle by 2.5
This leads to knew shapes that are 'based' on a shape mentioned above. For example, water has 4 electron pairs - 2bp and 2lp - so it is based on a tetrahedral structure. Each lone pair squeezes the bond angle by 2.5, so it has a bond angle of 104.5. This shape is known as v-shaped, angular, or bent.
3BP, 1LP - trigonal pyramidal, e.g NH3
4BP, 2LP - square planar