Ionic Compounds, Covalent Structures, Fullerenes and Metals

• Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces in all directions between oppositely charged ions. These compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds.
• When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and carry the current.

Properties of Ionic Compounds

Sodium Chloride:

• High melting point
• not conductive in solid state but when dissolved in water or molten, will conduct electricity

Magnesium Oxide:

• Higher melting point than sodium chloride because its ions have a greater number of charges, so they form stronger ionic bonds than than the ions in sodium chloride
• remains non-conductive because it stays solid at such high temperatures

Covalent Structures

Giant covalent structures contain many atoms joined by covalent bonds. They have high melting and boiling points. Diamond is a very hard substance because the carbon atoms in it are held very strongly to each other. However, graphite is soft because there are layers of atom which can slide over each other. They can do this because there are no covalent bonds between its layers. 

Graphite reduces rhe friction between two surfaces that are rubbing together by sliding over each other because they…