Graphite is a soft solid lubricant extremely difficult to melt. The reason for this anomalous behaviour is that graphite
(a) is a noncrystalline substance
(b) is an allotropic form of diamond
(c) has molecules of variable molecular masses like polymers
(d) has carbon atoms arranged in large plates of rings of strongly bound carbon atoms with weak interplate bonds.
(d) : Graphite has a twodimensional sheet like structure and each carbon atom makes a use of sp2 hybridisation.
The above layer structure of graphite is less compact than that of diamond. Further, since the bonding between the layers involving only weak van der Waal's forces, these layers can slide over each other. This gives softness, greasiness and lubricating character of graphite.
Correct option(d) has carbon atoms arranged in large plates of rings of strongly bound carbon atoms with weak interplate bonds.
Explanation:
C-atoms oi graphite form covalently bonded plates (layers) These layers are held together by weak forces of attraction. i.e., one layer can slide over other to cause lubricacy. lt cannot be melted easily as a large number of atoms being bonded strongly in the layer to form big entity.