Diamond Diamond has a very, very high melting point (about 4000°C) It does not conduct electricity at all (it is an insulator) The structure of diamond explains these facts….

This is a GIANT COVALENT NETWORK Each carbon is covalently bonded to FOUR others It is a tetrahedral arrangement There are NO MOLECULES This is a GIANT COVALENT NETWORK To melt diamond you need to break huge number of covalent bonds (which requires lots of energy) Carbon only has four electrons in its outer shell. These are all used in bonds so there are none free to conduct

Graphite Graphite has a very high melting point (about 3600°C) It conducts electricity well (though not as well as metals) The structure of graphite explains these facts….

This is also a giant covalent structure Each carbon covalently bonded to three others in LAYERS Van der Waals’ forces between layers Again, NO MOLECULES This is also a giant covalent structure To melt graphite, covalent bonds must be broken Although the weak van der Waals’ forces can be broken by pressing layers onto a page – writing in pencil Each carbon is only bonded to 3 others so there are free electrons between the layers that can move