Posted: Sun Nov 17, 2019 5:14 pm
For I3-, the shape is linear with 3 lone pairs around the central I atom. Why does the bond angle equal 180 degrees instead of being slightly below 180 degrees when there are 3 lone pairs of electrons around the central I atom? Wouldn't those lone pairs slightly push down on the bond angles?
Posted: Sun Nov 17, 2019 5:23 pm
I would try to visualize this in 3 dimensions. If there were no lone pairs, the molecule would have a trigonal bipyramidal shape with 180 degree bond angle through the axis and 120 degrees equatorial. But because there are 3 lone pairs, you remove the three equatorial atoms, causing enough repulsions to preserve the 180 degree bond angle. It's tricky but sometimes you just need to hard code the tendencies into your head XD