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 family elements are tetravalent in nature, since they have four electrons in their outermost shell. Since the ionization energy of carbon family elements are very high, M 4+ , as expected, hardly exists. On account of their low electronegativity, M 4- also do not exists.