Is the Lewis structure model enough to fully represent complex molecules?

[enter]

I do not know if uranium monoxide exists or not because I can't find anything about it on the internet, but i can make a lewis dot structure of it. Can somebody help about this?

 

[rootone]

The wiki article on Uranium does mention the compound UO as existing but says nothing of it's properties.
I found also one or two other references but not particularly useful., eg:
http://webbook.nist.gov/cgi/cbook.cgi?ID=C12035971&Mask=1000

 

[enter]

The wiki article on Uranium does mention the compound UO as existing but says nothing of it's properties.
I found also one or two other references but not particularly useful., eg:
http://webbook.nist.gov/cgi/cbook.cgi?ID=C12035971&Mask=1000

Thank you very much Rootone!

 

[Borek]

i can make a lewis dot structure of it

This is pretty weak argument, especially for block d and block f elements. Just because you can draw Lewis structure doesn't mean the compound exists, just like because you can't draw the structure doesn't mean the compound doesn't exist.

 

[Kekule]

just like because you can't draw the structure doesn't mean the compound doesn't exist.

Please elaborate. What sort of compounds are you talking about?

 

[Borek]

For example - any compound with electrons from orbitals other than s and p involved in the bonding. That means many compounds of transition metals.

 

[enter]

But how do i know if a compound (any compound) exists or not if i can't rely on the structure?

 

[Borek]

if i can't rely on the structure

Lewis dot structures are just a very simple model, reality is much more complicated. As of today the best predictive tool we have is a quantum mechanics - and its models give much better results. But even they don't always catch with the reality (although my understanding is that it is more a technical problem with solving QM equations, than a problem of QM being incorrect).

 

[Kekule]

I'm a practicing organic chemist and have a focus in organometallic compounds. I don't see how these transition metal complexes are different than any other compound when it comes to drawing their Lewis structures. More complicated for sure, but entirely able to be drawn. I'm skeptical of Borek's idea that they cannot be drawn. Please give a specific example.

 

[Quantum Defect]

I'm a practicing organic chemist and have a focus in organometallic compounds. I don't see how these transition metal complexes are different than any other compound when it comes to drawing their Lewis structures. More complicated for sure, but entirely able to be drawn. I'm skeptical of Borek's idea that they cannot be drawn. Please give a specific example.

I guess I am with Borek. Lewis Electron Dot structures are a simplification for understanding the bonding in molecules. If you look at Lewis' original paper on the subject, he even proposes that the octet rule may have something to do with an atom being cubical, with electrons at the vertices.

Over the years, the Lewis structure idea has been expanded to deal with things like resonance structures, aromaticity, two-electron-three-center bonds, expanded octets, etc. These are all kind of patches on the original model that have been made to deal with new discoveries. With something that has evolved as much as "Lewis Structure" has, you need to define which model you are talking about.

The ability to draw a Lewis Dot Structure that fulfills all of the rules for these kinds of structures gives you some idea that the molecule may be stable, but it is not definitive. I can draw some Lewis structures that satisfy the Lewis structure rules for being ok, that nevertheless represent highly unstable molecules (think about some highly strained ring systems).

Similarly there are relatively stable (also we need to define what "stability" means) molecules for which the Lewis Structure rules do not predict a "good" structure. E.g. there is lots of (H3)+ in the universe, but I don't think that you can use Lewis Structure rules to draw its most stable structure.

Lewis structures ==> a useful model with the ability to give you useful answers about the structures of many molecules, but by no means the last word on the subject

 

[Kekule]

...the Lewis structure idea has been expanded to deal with things like resonance structures, aromaticity, two-electron-three-center bonds, expanded octets, etc.

Lewis structures ==> a useful model with the ability to give you useful answers about the structures of many molecules, but by no means the last word on the subject

Which is exactly what I was talking about in my last post. There are ways to draw the different complexes that do a pretty good job of describing the molecule. But like any model, there are limitations to what it can actually represent.

I would agree that, "just because you can draw the structure, doesn't mean the compound exists or is stable." But I would not agree with, "just like because you can't draw the structure doesn't mean the compound doesn't exist." You can always draw something. That might mean adding an addendum to the Lewis Structures model, but it's still possible.