(Polar molecules, Non-polar molecules, etc.)
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I believe that Professor Lavelle said we don't need to know the exact bond angles for specific molecules, but we should know it for the general shape. So if you identify a molecule to have the trigonal pyramidal shape (3 bonding pairs and 1 lone pair), you can say that the bond angles for that molecule are slightly less than 109.5 since a tetrahedral (4 bonding pairs) has bond angles of 109.5.
The questions will likely ask us to estimate the bond angles, in which case we would take into account the positioning of the lone pair electrons. Depending on where the lone pair electrons are, we can estimate if the bond angle is greater than or less than the standard shape's angle.
It isn't necessary to memorize exact bond angles for specific molecules. Dr. Lavelle mentioned that we just need to know how lone pairs affect repulsion and nearby bond angles (i.e. a lone pair will push against adjacent bond angles, making them less than the standard degree for that specific shape).
For this, is there a way to calculate or memorize bond angles when there is a lone pair? It is usually slightly different than the angles of the normal structure. Is there a set degree amount that a lone pair shifts a bond?
Jennifer Lathrop 3E wrote:For this, is there a way to calculate or memorize bond angles when there is a lone pair? It is usually slightly different than the angles of the normal structure. Is there a set degree amount that a lone pair shifts a bond?
There's no set amount of change I believe. I just know that the more lone pairs there are, the stronger the repulsion away from them and therefore the smaller the angle gets. There is a chart with the exact angles if you's like to memorize them!
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