Why is the structure of graphite significant for its properties?

The significance of graphite's structure lies in the way its atoms are arranged, specifically in layers of carbon atoms bonded together in a two-dimensional hexagonal lattice. Each layer consists of carbon atoms bonded to three other carbon atoms through strong covalent bonds, while the fourth outer electron is delocalized. This delocalization allows the electrons to move freely across the layers.

The layers are held together by weaker van der Waals forces, which means they can easily slide over one another. This characteristic makes graphite useful as a lubricating material and allows it to be used in applications such as pencils, where the ability to slide easily is essential for leaving marks on paper.

The other options do not correctly represent the properties that arise from graphite's structure. While graphite does have high tensile strength due to the strong covalent bonds within the layers, it is the layered structure that primarily enables its unique sliding property. Graphite is also a good conductor of electricity because of the delocalized electrons, contradicting the idea that it creates a non-conductive material. Furthermore, the delocalised electrons are a key feature of graphite’s ability to conduct electricity; therefore, limiting this delocalisation would not align with graphite's known properties.