Why are Diamond and Graphite insoluble?
Diamond has a giant covalent structure, its carbon atoms are each covalently bonded to four other carbon atoms, and because covalent bonds are very strong it takes a lot of energy to break each bond, this makes diamond really hard. Graphite is also a giant covalent structure but each carbon atom only forms 3 covalent bonds. Graphite does have free electrons because this is what allows it to conduct electricity.
