• An allotrope is a different structural form of the same element in the same physical state, where the atoms are arranged differently, giving rise to distinct physical and chemical properties.
• Both diamond and graphite are made entirely of carbon atoms and have high melting points due to strong covalent bonding.
• However, they differ in bonding arrangement: diamond has a 3D tetrahedral network (hard, non-conductive), while graphite has layered structures with delocalised electrons (soft, conductive).

• Allotropes are different structural forms of the same element in the same physical state.
• For example, diamond and graphite are both made entirely of carbon atoms but differ in atomic arrangement and bonding: diamond has a 3D tetrahedral network of covalent bonds, while graphite has layers of hexagonally arranged atoms held together by weak dispersion forces.
• Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
• For example, carbon-12 and carbon-14 are isotopes of carbon; both have 6 protons, but carbon-12 has 6 neutrons while carbon-14 has 8 neutrons, giving it radioactivity.

Graphite:

• Graphite consists of layers of carbon atoms arranged in a hexagonal lattice.
• Each carbon atom is bonded to three others in the same plane, with delocalized electrons between layers.
• The weak intermolecular forces between these layers allow them to slide over each other easily, contributing to graphite’s softness and its use as a lubricant. 

Diamond:

• In contrast, diamond features a three-dimensional lattice where each carbon atom forms four strong covalent bonds with other carbon atoms, arranged in a tetrahedral structure.
• This extensive network of strong bonds throughout the lattice makes diamond one of the hardest natural substances, leading to its use in cutting and drilling tools.