If you struggle to memorize molecular bond angles, I highly recommend this video. It visually explains how electron pairs repel each other using clean 3D graphics, saving you from mindless memorization.
To figure out a 3D shape, you must start by drawing the 2D Lewis structure. The video notes that a double bond is simply counted as a single electron domain.
Electrons have negative charges and strongly repel each other. The creator compares this to strangers in a crowded elevator trying to stand as far apart as physically possible. This repelling force is what actually determines the 3D shape of the molecule.
The default is a flat triangle spread out at 120 degrees. But when a bulky lone pair of electrons sneaks in, it presses down on both sides. You can see this create a narrower Bent structure at [Time 03:06].
This forms a 109.5-degree tetrahedral structure stretching into 3D space. As lone pairs are added, the downward pressure gets heavier, visibly shrinking the bond angles from Trigonal Pyramidal at [Time 03:34] to a Bent shape at [Time 03:51].
Things get complicated with 5 or more domains, but the video's 3D graphics make it super intuitive. Lone pairs will always take the spots with the most empty space. The animations perfectly demonstrate how this creates unique structures like the Seesaw at [Time 04:31], the T-shape at [Time 04:52], and even the perfectly flat Square Planar at [Time 06:29].
Check out the visual 3D animations for a much better understanding!
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