The study of the deltahedral structures of this element’s hydride clusters motivated the development of polyhedral skeletal electron pair theory. Two banana-shaped bonds appear in a compound consisting of two atoms of this element and six hydrogen atoms; those bonds are three-center two-electron bonds. (-5[1])The hexagonal form of this element’s nitride has a structure analogous to graphene. With the halogens, this element forms trigonal planar compounds that are considered “electron-deficient,” such as a trifluoride (10[1])that violates (10[1])the octet rule. For 10 points, name this lightest metalloid element with atomic number five, (10[3])symbolized (10[1])B. (10[1])■END■ (10[1]0[1])