polyhedra with n vertices trigonal bipyramid octahedron pentagonal bipyramid N=5 N=6 N=7 dodecahedron tricapped trigonal prism N=8 N=9 bicapped square antiprism N=10 icosahedron N=12 octadecahedron 16.8 N=11 "Closo"series -formula BH2- Total valence electrons(CVE)=3n(from B)+n(from H) +2 (negative charge)=4n+2 Each BH unit uses 2 electrons.Hence skeletal or framework electrons (NFE=4n+2-2n=2n+2) There is little tendency to add H+and form neutral species. The closo species are,in effect,the anions of quite strong acids. Structures are those of the appropriate polyhedra with n vertices.polyhedra with n vertices “Closo” series -formula BnHn 2- Total valence electrons (CVE) = 3n (from B) +n (from H) +2 (negative charge) = 4n+2 • Each BH unit uses 2 electrons. Hence skeletal or framework electrons (NFE=4n+2-2n=2n+2) • There is little tendency to add H+ and form neutral species. The closo species are , in effect, the anions of quite strong acids. • Structures are those of the appropriate polyhedra with n vertices