the non-metals boron, carbon, and silicon form giant covalent lattices
carbon and silicon use their four outer electrons to form covalent bonds to other carbon and silicon atoms
diamond forms a tetrahedral arrangement of the carbon atoms so has a bond angle of 109.5 by electron-pair repulsion
high melting and boiling points as the covalent bonds are strong meaning high temperatures are needed to break them to provide the large quantity of energy
insoluble in almost all solvents as the covalent bonds are too strong to be broken by interactions with solvents
don't conduct electricity except graphene and graphite
in diamond and silicon all four outer electrons are involved in covalent bonding so none are available for conducting electricity
graphene and graphite are both giant covalent structures of carbon based on planar hexagonal layers with bond angles of 120 by electron-pair repulsion
