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 (10[1])appear in a compound consisting of two atoms of this element and six hydrogen atoms; (-5[1])those bonds are three-center two-electron bonds. The hexagonal form of this element’s nitride has a structure analogous (10[1])to graphene. With the halogens, (-5[1])this element forms trigonal planar compounds that are considered “electron-deficient,” (10[2])such as a trifluoride that violates the octet rule. For (10[1])10 points, name this lightest metalloid element (10[1])with atomic number five, (10[2])symbolized B. ■END■ (10[2])