"hypervalent and hypercoordinate" . "hypervalent molecule" . . "hypervalent species" . . "pentacoordinate" . "Hypervalency" . "Hypervalent bonding" . "Hypervalent molecule" . "N-X-L nomenclature system" . "Hypervalent molecule#N-X-L notation" . . "expand its octet" . "hypervalence" . . . "Hypervalent molecule" . "ab initio molecular orbital calculations" . "hypervalent" . "Pentacoordinated silicon" .