Final answer:
Graphite is a polymorph of diamond; they are both forms of carbon with differing structural arrangements. Graphite is soft, slippery, conducts electricity, and is used in pencils due to its property of being less dense and having layers held by weaker forces compared to the rigid, extremely hard structure of diamond.
Step-by-step explanation:
Graphite is a polymorph of diamond, meaning they are two structural forms of the same element, which is carbon. Unlike diamond, graphite is not an ore of lead, nor is it composed of pure silicon, and it is also softer than glass. Graphite has a layered structure with carbon atoms arranged in a trigonal planar formation. Each carbon atom is connected to three others within its layer by strong covalent bonds, and the layers are held together by weaker van der Waals forces. This arrangement makes graphite soft enough to be used in pencils to leave marks on paper, as artists often utilize it based on its varying degrees of hardness influenced by the ratio of clay binder mixed with it. Furthermore, graphite conducts electricity and is very different from diamond, which is the hardest-known natural substance composed entirely of carbon atoms in a dense network.