Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In chemistry a trigonal bipyramid formation is a molecular geometry with one atom at the center and 5 more atoms at the corners of a triangular dipyramid. This is one of the few cases where bond angles surrounding an atom are not identical (see also pentagonal dipyramid), which is simply because there is no geometrical arrangement which can result in five equally sized bond angles in three dimensions.