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So basically according to university textbooks, it is said that the second lone pair in a trigonal bypyramidal arrangement would also reside on the trigonal plane, causing the two lone pairs to be beside each other and compressing the other 3 bonded pairs (resulting in T-shape).
However, my question is: Why doesn't the two lone pairs move to the two axial groups so that the the three bonded pairs reside on the trigonal plane? Surely this would result in the less repulsion within the arrangement? Wouldn't the repulsion between a lone pair and 3 bonded pairs at 90 degrees be less than the repulsion between a lone pair and another lone pair & 3 bonded pairs?