Hi,
I saw an exam question to which I can't find the answer. The question was (among other things)
“why does graphite have a high boiling point?”
My answer is
Graphite is held together by two different types of force
1)Every carbon atom is covalently bonded to three other atoms in a “sheet”. These bonds are sp2 hybrids. The bond angle is 120 degrees
2)The remaining p-orbital electron in carbon is delocalised between the atoms and in fact move between the sheets of carbon
The force resulting from the delocalised electrons is the relatively weak Van der Waals force.
Melting point and boiling points are determined by the strength of bonds between atoms and molecules. One would expect VdW forces as weak to make m.p. Graphite to be low. However, in a sample of graphite there are billions of such bonds between the sheets of carbon. Hence their aggregate effect is large causing a high m.p.
Does that seem a reasonable (correct) argument?
Thanks
Clive