Question

which are three Allotropes of Carbon ?

Answer 1

The various physical forms in which an element can exist are called allotropes of the element. The Carbon element exist in three solid forms called allotropes:

1. Diamond
2. Graphite   and 
3. Buckminsterfullerene

Diamond and Graphite are the two common allotropes of carbon known to us for centuries. Buckminsterfullerene is the new allotropes discovered recently.
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Answer 2

Hi !
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Three allotropes of carbon are :

diamond 

Graphite 

Fullerene 
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Diamond is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice.

Graphite is a crystalline allotrope of carbon, a semimetal, a native element mineral, and a form of coal. Graphite is the most stable form of carbon under standard conditions.

A fullerene is a molecule of carbon in the form of a hollow sphere, ellipsoid, tube, and many other shapes. Spherical fullerenes, also referred to as buckyballs, resemble the balls used in association football.
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