(Polar molecules, Non-polar molecules, etc.)
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Bond angles are determined by the largest angle between to atoms in a molecule. It is dependent on how many bonds are in the molecule. For example, a molecule with two bonds coming off of the central atom will be linear, as a 180 degree angle is the largest possible angle between these two bonds.
bond angles are the angles between two bondings in a atom (consider the bondings as lines and the central atom as the point). I think we can predicts them by putting atoms to achieve a most stable structure (basically by putting the atoms bound to the central one as far apart as possible), and calculate the angles (if we can).
To identify bond angles and shape, locate the central atom and see how many bonds are connected to it. You also have to count the lone pairs as bonds. If the number of bonds is 2, the shape is linear and angles are 180 degrees. If the number of bonds is 3, then the shape is triagonal planar and angles are 120 degrees. If the number of bonds is 4 then the shape is tetrahedral and angles are 109 degrees. etc etc
Shundeen Martinez 1D wrote:Also when can we know that bond angles are less than what they usually are? Like I remember in lecture Lavelle said a bond angle was 106.5 degrees.
I think the one he was talking about was SO_3^2- (sulfite). By drawing the lewis structure, we see that the central atom, S, has 4 regions of electron density (1 lone pair and 3 bonds). This makes the shape trigonal pramidal. If it were tetrahedral, the bond angle would be 109.5, but because the lone pair wants to be as far away as possible, it pushes the 3 bonds away from it. This pushes the bonding pairs closer to each other, making the angle <109.5, or 106.
Yes I believe we are supposed to remember bond angles. I think the easiest thing to do is memorize them, but you can always try to visualize by drawing out the Lewis structure. That may get frustrating on a test with limited time though.
Hedi Zappacosta 4H wrote:Bond angles are determined by the largest angle between to atoms in a molecule. It is dependent on how many bonds are in the molecule. For example, a molecule with two bonds coming off of the central atom will be linear, as a 180 degree angle is the largest possible angle between these two bonds.
Thank you and Can you give another example?
Brice McKeown 3D wrote:Why is it that molecules with the same VESPR formula and lone pairs present have different bond angles? For example, look at the VESPR formula AX2E. O3 has bond angles of 116.8, but SO2 has bond angles of 119.5.
I see thank you.
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