How does electronegativity affect bond strength????????????????????

reyrey389

whats the strongest bond polar covalent, nonpolar covalent, or ionic
how does electronegativity affect bond strength

some people say the more electronegative the molecule the stronger the bond, so than shouldnt ionic bonds be stronger than covalent bonds? just doesnt make sense.........

DrDu

Bond strength depends on many factors like e.g. the size of the atomic orbitals which form the molecule. You have to state first which of these other parameters you want to keep constant for your question to make sense.
E.g. if you replace one atom in a homonuclear covalent bond with another atom with comparable orbitals but higher or lower EN this tends to weaken the bond.

samblohm

The farther away the electronegativity of 2 atoms, the stronger the bond generally. Cesium has the lowest, and Fluorine has the highest and the make the strongest ionic bond (well single bond at least). The strongest polar covalent that I can think of is the Carbon-Fluorine bond. And yes ionic bonds are stronger than covalent bonds. Just look at melting points. Ionic compounds have high melting points and covalent compounds have low melting points.

And a good amount of what I said is just in general.

reyrey389

ye ur right ionic is stronger, i asked my teacher. also how do you determine reactivity from the lewis structures? like how are alkenes more reactive than alkanes when alkenes contain double bonds?

doesnt strong bonds imply less reactivity?

thanks

samblohm

The reason alkanes don't react is because they are don't have any functional groups. A hydrogen-carbon bond is a more stable alternative to a carbon-carbon double bond. The strength of 2 hydrogen carbon bonds is stronger than one carbon carbon double bond.

And it's kinda tough come up with a rule to determine reactivity from lewis structures.

DrDu

Carbon: >3500K , Silicium: 1410 K, Boron:2300 K, CsF: 955 K

samblohm

Were talking about compounds, not elements so what you listed doesn't apply.

Borek

SiC 3000K, WC 3143K, SiO₂ just below 2000K.

samblohm

I suppose your right, those are covalently bonded, but I personally would consider them covalent networks vs a more common organic covalent bond. But, like I said, they really are covalent bonds.

DrDu

Why? I thought we were talking about covalent vs. ionic bonds. A purely covalent bond is easiest to observe in elements.

samblohm

Although they are covalent bonds, I would consider those to be covalent networks instead of standard organic covalent bonds.

DrDu

What is probably also helpful in this discussion is the definition of electronegativity by Pauling:
http://en.wikipedia.org/wiki/Electronegativity
You can see that it is the additional stabilization of the heteronuclear bond as compared to the homonuclear bonds.

sjb-2812

And the bonding in e.g. halite is not a network too?

samblohm

Halite is made of ionic bonds, so it isn't a covalent network

Borek

You missed the point of the question. Sjb didn't ask if it is a covalent network, but whether it is a network. Substantial difference.

samblohm

ok, I think I understand now. Instead of classifying melting point by covalent or ionic bonds, could they be classified by whether or not they are a network?