The Prefix is Otterbox's least expensive iPhone case. The durable silicone, polycarbonate skeleton build of the OtterBox Prefix is thicker than the Commuter and Reflex, but also the least protective. The Prefix is a one-piece case, meaning that it does not snap in place like the Reflex .
carbon is considered tetravalent because it has four valence electrons the valence electrons are in the outermost shell of the atom and allows carbon to form four bonds to other atoms
Carbon compounds are much more covalent than analogous compounds of silicon, germanium, tin, or lead. Even more significantly, carbon forms double and even triple bonds with itself or other elements, forming compounds that the heavier elements of this group cannot form like acetylene (C2H2). Silicon and the heavier elements of this group can form only single bonds.