Three nitrogen groups are bound to this element in alternative coupling agents used in solid-phase peptide synthesis, such as B·O·P and Py·B·O·P. A method of activating a palladium zero catalyst for the Heck reaction involves acetate forming a bond with this element. Nickel complexes to ligands containing this element were used to develop the Tolman cone angle parameter. Berry (*) pseudo-rotation is classically exemplified by this element bound to five fluorine atoms. Many courses incorrectly teach that oxygen binds to this element in a betaine (“beta-een”) intermediate [emphasize] after a carbon-carbon bond forms in the Wittig reaction. For 10 points, name this element that sits right below nitrogen on the periodic (10[1]-5[1])table. ■END■ (10[1]0[1])