Le Bel in the same year (1874), independently
argued that the spatial arrangement of four groups (valencies)
around a central carbon is tetrahedral and if all the substituents
attached to that carbon are different, the mirror image of the
molecule is not superimposed (overlapped) on the molecule;
such a carbon is called asymmetric carbon or stereocentre The resulting molecule would lack symmetry and is referred to
as asymmetric molecule The asymmetry of the molecule along
with non superimposability of mirror images is responsible for
the optical activity in such organic compounds The symmetry and asymmetry are also observed in many day to day
objects: a sphere, a cube, a cone, are all identical to
their mirror images and can be superimposed