Giant covalent structures

Graphite is a form of a carbon that has a giant covalent structure (lattice). Unlike diamond, each carbon atom in graphite only forms three covalent boncds with other carbon atoms. This means that graphite has a layered structure with strong bonds between carbon atoms and weak intermolecular forces between layers. The layers can slide over each other because of the weak intermolecular forces, making graphite soft and slippery.

Because each carbon atom in graphite forms only five bonds, one electron from each atom is delocalised. These delocalised electrons are free to move and therefore graphte conducts electricity. It is the only non-metal element to do this.

Silicone dioxide (SiO2, also known as silica) has a giant, rigid covalent structure (lattice) similar to diamond, where each oxygen atom is joined to two silicon atoms and each silicon atom is joined to four oxygen atoms.

The large number of strong covalent bonds results in silicon dioxide having a very high melting point.

Diamond is a form of carbon that has a giant, rigid covalent structure (lattice) where each carbon atom forms four covalent bonds with outher carbon atoms.

The large number of strong covalent bonds results in a diamond having a very high melting point and which makes diamonds very hard.

A giant ionic structure is a regular structure (giant ionic lattice) held together by the strong forces of attraction electrostatic forces) between oppositively charged ions. These forces act in all directions in the lattice. This results in them having high melting and boiling points because large amounts of energy are required to break the strong ionic bonds.

Ionic compunds conduct electricity when molten or in solution because the charged ions are free to move about.

Gases, liquids and solids that have relatively low melting and boiling points consist of simple molecules. Because their molecules have no overall electric charge, they do not conduct electricity.

Simple molecular substances have low melting and boiling points because they have weak forces between molecules (intermolecular forces). It is these intermolecular forces that are broken when the substance melts or boils, rather than the strong covalent bonds holding the atoms together.

Ionic bond- electrostatic attraction between positive metal ions and negative non-metal ions

Covalent bonds- when non-meta atoms share electrons 

Metallic bonds- are attraction between delocalised electrons and positive metal ions, they occur between metal atoms only