Understanding Covalent Bonds: Why Do They Hold Molecules Together?

[RichyOwen]

I took chemistry a couple years ago but never got a satisfactory answer as to why covalent bonds hold molecules together. I understand that they share their outermost electrons, but why would that keep them together? Do the electrons pull against each other or something?

 

[DrChinese]

Welcome to PhysicsForums, RichyOwen!

A simple way of considering it: if two positive nuclei are attracted to the same negative electron, and that attractive force exceeds the repulsion of the two positive nuclei, then net attraction means the nuclei form a covalent bond.

That binding energy is not very strong compared to the binding of positively charged protons and neutrons due to the strong force within the nucleus, of course.

 

[RichyOwen]

Thanks so much! I was quite puzzled. Do you know if covalent theory is accepted by most quantum physicists?

 

[RichyOwen]

Also, will the two nuclei then be the same distance (on average) from the shared electron?

 

[DrDu]

Thanks so much! I was quite puzzled. Do you know if covalent theory is accepted by most quantum physicists?

Yes, it is. The question would have been maybe more apt for the Atomic, solid state, comp phys forum.
One of the best explanations of covalent bonding in my opinion is given in this article by Kutzelnigg:
http://onlinelibrary.wiley.com/doi/10.1002/anie.197305461/abstract

 

[RichyOwen]

Sorry I'm new to this forum stuff. Thank you!