What is the difference between trigonal pyramidal molecular shape vs. trigonal planar molecular shape? Why does the bond angle change between these molecular shapes when they both
include 3 attached atoms?

Explained below.

Explanation:

- The difference in shape is that in the form of 3D view, trigonal planar resembles a flat triangle, while trigonal pyramidal looks like a pyramid.

- For trigonal planar, the bond angle is 120°, whereas in trigonal pyramidal, the bond angle is 107°. This lesser in trigonal pyramidal due to the lone pair that subdues the bonding pairs that are hybridized whereas in trigonal planar, there is no lone pair.

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