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What happens to the intramolecular bonds when a network covalent substance is melted? I understand that in covalent molecular substances, the intermolecular bonds weaken between the molecules once molten. My confusion is with what happens to the bonds between network covalent substances when melted.

  • Do the intramolecular bonds break, leaving only the individual atoms (carbon for example in graphite or diamond).
  • Do the intramolecular bonds weaken The basis for this query is when I was asked to predict the electrical conductivity of graphite and silicon dioxide in molten states (Graphite sublimates, but under pressure is liquid). I started by researching the atomic and bonding structure of the elements when they are melted but could find very little information.

TLDR: What happens to covalent network bonds when they melt

Thankyou

hayne newell
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    The nature of liquid carbon can't be explained in a few words, and besides, isn't even known all that well. – Ivan Neretin Mar 19 '20 at 07:23
  • @IvanNeretin thankyou, I rabbit holed a bit on a highschool assignment. I became very curious about it. Thankyou for pointing me towards liquid carbon, that should have more results than "help! Network covalent melting does what!?!?" – hayne newell Mar 19 '20 at 07:28
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    Here are some previous related questions: (1) (2) – Nicolau Saker Neto Mar 19 '20 at 09:56
  • Silica is melting at a rather high temperature, because the whole crystal is made of a huge molecule, where each atom is attached to the whole structure by covalent bonds. All silicium atoms are attached by four sigma bonds to different Oxygen atoms. And all Oxygen atoms are attached by two sigma bonds to two different Si atoms. So the whole structure is rigid, and it is difficult to break all the bonds Si-O simultaneously. – Maurice Mar 19 '20 at 10:31
  • " intramolecular bonds break, leaving only the individual atoms (carbon for example in graphite or diamond)" - that like never happens. Even in gas phase there are usually small molecules. – Mithoron Mar 19 '20 at 15:46
  • @Mithoron oh ok, so how are molecules formed in a molten network covalent substance? – hayne newell Mar 19 '20 at 19:46
  • Some bonds are weakened, some get broken even before melting, some with further heating. That's complicated and highly case dependant. – Mithoron Mar 19 '20 at 20:11
  • @Mithoron ah alright, I guess I was trying to pigeon hole a complex question – hayne newell Mar 19 '20 at 20:12

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