Concept:The electrical conductivity of carbon allotropes depends on the arrangement of carbon atoms and the availability of free (delocalized) electrons.
Explanation:Diamond has a rigid tetrahedral structure where each carbon atom forms four strong covalent bonds.
All valence electrons are used in bonding, leaving no free electrons to conduct electricity.
Hence, diamond is a poor conductor of electricity.
Graphite has a layered structure where each carbon atom is bonded to three others, forming hexagonal sheets.
The fourth valence electron is delocalised and can move freely between the layers.
This free electron cloud makes graphite a good conductor of electricity.
Fullerenes (e.g., buckyballs, nanotubes) are cage‑like molecules with carbon atoms arranged in pentagons and hexagons.
Although some fullerenes like carbon nanotubes can exhibit conductive properties, pure fullerenes are generally semiconductors or insulators at room temperature.
They are not considered good conductors in the same category as graphite.
Therefore, only graphite is a good conductor of electricity among the three allotropes listed.
Answer:2 only (Graphite)
