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T-shaped vs trigonal planar

Posted: Sat Dec 08, 2018 12:11 pm
by Kassidy Tran 1E
When do you know whether to place the lone pairs on the equatorial axis instead of the axial axis? For example, for ICL3 which has the VSEPR formula AX3E2, why do we place the two lone pairs on the equatorial axis (resulting in T-shaped molecule) instead of placing them opposite of the other on the axial axis?

Re: T-shaped vs trigonal planar

Posted: Sat Dec 08, 2018 12:31 pm
by Alexandra Albers 1D
I believe that when you have 5 regions of electron density, you always want to replace the equatorial areas with lone pairs before the axial. For Ax4E, you would replace the equatorial to get a seesaw, for AX3E2 you would replace the equatorial for T-shape, and for AX2E3, you would replace all equatorial areas to get linear. This method likely ensures that the the regions are as far from each other as possible.