TRIGONAL PYRAMIDAL (AX3E)

This is an example of a trigonal pyramidal molecule. These molecules have four atoms in the shape of a pyramid with a base in the shape of a triangle. AX3E signifies that the molecule has a lone electron pair around the central atom. This lone pair is pushed away from the adjacent atoms and exists around the central atom. An example of a trigonal pyramidal molecule is ammonia, NH3, which has a nitrogen atom as its central atom, and three hydrogens surrounding it, forming the "base of the pyramid." In this case, the angles are equal to each other, but because it is not a planar molecule, the angles will not add up to 360 degrees. Some trigonal pyramidal molecules will not have a symmetrical base because the angles will not all be the same. For example, methylamine, NH2CH3, has a nitrogen as its central atom, and is surrounded by two hydrogen atoms and a CH3 group. This molecule does not have a symmetrical base. Its angles are 112.2, 112.2, and 105.8 degrees respectively.

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