Allotrope of an element means ‘different structural arrangement of that element’.
The popular allotropes of carbon are- Diamond, Graphene, Fullerene
There are many other forms of carbon also available like Lonsdaleite.
(a) represents the structure of diamond, where each carbon is linked with four other carbon atoms forming a tetrahedron.
In diamond, each Carbon atom is sp3 hybridised.
(b) represents the structure of graphene. (There are four graphene units in the above picture) Graphene units piles up on one another to form graphite. That means graphite is a polymer of graphene.
Each carbon atom in graphene is sp2 hybridized. As a result of which there is one electron in nonbonding orbital. That is why it can conduct electricity (due to availability of free nonbonding electron).
Graphite consist of layers of graphene units. The distance between any two layer is 0.335 nano meter.
(c) represents Lonsdaleite. It is also called ‘Hexagonal Diamond’ because of its hexagonal close packing of arrangement. It forms when meteorites containing graphite strike the Earth. The great heat and stress of the impact transforms the graphite into diamond, but retains graphite’s hexagonal crystal lattice.
(g) represents amorphous form of carbon. Its property depends on the ratio of sp2 and sp3 hybridised carbon present in the material.
It lacks ordered arrangement of carbon.
d, e, f, h ——> fullerene
Fullerenes (also called buckyballs) are molecules of varying sizes composed entirely of carbon that take on the form of hollow spheres, ellipsoids, or tubes.
(h) can also be called as ‘carbon nanotubes’…
1. The surface of diamond is lipophillic (oil loving) and hydrophobic (water hating), which means it cannot get wet by water but can be in oil.
2. Graphite has a thermal conductivity upto 3500 °C
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