### geometric angles

Posted:

**Sun Nov 17, 2019 4:38 pm**How do you determine the angles in a structure (i.e. 180 degrees of 109.5 degrees)?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=41&t=51867

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Posted: **Sun Nov 17, 2019 4:38 pm**

How do you determine the angles in a structure (i.e. 180 degrees of 109.5 degrees)?

Posted: **Sun Nov 17, 2019 4:43 pm**

The angles can only be determined experimentally but if there is no lone pair, each type of VSEPR structure has specific angles in between the bonds. To do this, you can only memorize the angles for more complex shapes such as tetrahedral... But for other shapes such as linear, the angles have to add up to 360, which makes the bond angle 180 between the atoms and in trigonal planar, 360/3=120.

Posted: **Sun Nov 17, 2019 5:00 pm**

Geometric angles in bonds are experimentally found. You can memorize the angles for each molecular shape, but each angle varies slightly as a result of lone pair interactions that are unique to each molecule. We're not expected to memorize the angles, but just know how to determine whether one angle is greater or less than another angle as a result of interactions within the molecule.

Posted: **Sun Nov 17, 2019 5:04 pm**

In the shapes without lone pairs, the angles are fairly simple; usually the 360 divided by the amount of elements bonding.. when there is a lone pair on the central atom, that changes. The angles of the structures will vary as a result of the new high electron density region

Posted: **Sun Nov 17, 2019 5:05 pm**

^^^ the geometric angles correspond with the VSEPR chart which depends on how many bonding pairs and lone pairs you have. for example a structure with 2 bonding pairs and 2 lone pairs would be bent and would have bond angles of less than 109.5 because of the lone pairs “pushing” on the angles in the structure