Answer:
In diamond the carbon atoms are covalently bonded as flat sheets
In silicon(IV) dioxide the silicon and oxygen atoms are covalently bonded in flat sheets
The structure of copper includes a lattice of positive ions
Step-by-step explanation:
Diamond and silicon(IV) dioxide are covalent network solids. Covalent network solids are made up of atoms joined to one another by covalent bonds to form a giant lattice, The solids are hard and have a very high melting point. They do not conduct electricity. So, for both diamond and SiO2, atoms are covalently bonded to yield flat sheets in a covalent bonded network solid.
Copper is a metallic substance having metallic bonds, a metallic crystal consists of positive ions and a cloud of electrons.