Question

What are three forms of the element carbon?

Answer 1

Graphite, diamond, and the fullerenes?

Explanation:

See here for a link to the fullerenes. All of these are carbon allotropes; they consist only of the element carbon but have different connectivities between atoms. Buckminsterfullerene, `C_60`, which I think you can buy relatively cheaply, has the molecular shape of a geodesic sphere.