Question

carbon exist in different allotropic form why

Answer 1

Due to
1)catenation
2)tetra valency

Of carbon atom

Answer 2

Carbon exists in several structurally different forms, out of which the three widely studied allotropes of carbon are graphite, diamond, and amorphous carbon.The former refers to occurrence of two or more atoms of the same element having different number of neutrons; whereas the latter is defined as occurrence of an element in two or more structurally different forms.