Ionic character & strength

[SaintJude]

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Why are bonds with a greater ionic character (greater electronegative difference) relatively stronger?

For example, O-H bond is stronger than the N-H b/c O-H has a "greater ionic character" .

 

[MedPR]

Why are bonds with a greater ionic character (greater electronegative difference) relatively stronger?

For example, O-H bond is stronger than the N-H b/c O-H has a "greater ionic character" .

It's simple when you consider the same metal bound to different nonmetals; the more electronegative the nonmetal, the more it wants the electron(s) from the metal. Hence HF is stronger than H-anything else.

Also, you can think of it in terms of lattice strength. If you put a bunch of OH molecules together, each molecule would have a dipole with the electron density almost exclusively on the oxygen. This means that when another OH gets close, its H is going to be attracted to the other molecule's O. As you bring more and more of these together, the interaction gets stronger.

The same concept applies if you have two ionic compounds with a different metal and a different nonmetal. The more "ionic character" (difference in electronegativity) the more the two will want to hang on to each other. Sodium doesn't really want its electrons, and if it is near a Cl, the Cl will happily take them. Both of them are happy and have no reason to seek out another partner, but if a flirty Fluoride comes around, then slutty Sodium (lol, sorry I'm really bored) is going to jump right on her and leave the relatively charming Chloride.