Jump to content
Sign in to follow this  

Question about structures of ionic solids with partial covalent character

Recommended Posts

Hey guys,

 

So in Energetics HL, we learn that a significant difference between theoretical and experimental lattice enthalpies indicates partial covalent character. And this depends on the electronegativity difference basically, like AgCl for example, there is partial covalent character and the difference is huge. 

 

The thing is, in my head, I picture an ionic solid as a lattice and a covalent one as simple molecular. I've seen a chart with EN difference vs. %ionic character, but how do we determine the structure. Where is the sort of, ratio of ionic to covalent when the solid is a lattice, and then becomes a covalent compound with a strong dipole? I know its a continuum but a lattice is a very specific thing and I'm finding it hard to picture a partially covalent lattice.

 

Can someone help me out here?

 

Thanks :)

 

Edit: I found this on Wikipedia: It is important to recognize that clean ionic bonding – in which one atom "steals" an electron from another – cannot exist: All ionic compounds have some degree of covalent bonding, or electron sharing. Thus, the term "ionic bonding" is given when the ionic character is greater than the covalent character—that is, a bond in which a large electronegativity difference exists between the two atoms, causing the bonding to be more polar (ionic) than in covalent bonding where electrons are shared more equally.

 

I knew this, but in terms of structure, when does the change from lattice so molecules held together due to dipoles occur?

 

I found this answer: However, even if ionic bonding is combined with some covalency, the result is not necessarily discrete bonds of a localized character. In such cases, the resulting bonding often requires description in terms of a band structure consisting of gigantic molecular orbitals spanning the entire crystal. 

 

But the question remains, where is the threshold :P

Edited by Ossih

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.