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
The symmetry of a molecule (or any other object) determines whether it is chiral. A molecule is achiral (not chiral) when an improper rotation, that is a combination of a rotation and a reflection in a plane, perpendicular to the axis of rotation, results in the same molecule.For tetrahedral molecules, the molecule is chiral if all four substituents are different.A tetrahedral molecule can be chiral while its four substituents are identical. A chiral molecule is not necessarily asymmetric (devoid of any symmetry element), as it can have, for example, rotational symmetry. molecule can have multiple stereogenic centers without being chiral overall if there is a symmetry between the two (or more) stereocenters themselves. Such a molecule is called a meso compound. It is also possible for a molecule to be chiral without having actual point chirality.