electronegativity/reactivity

[max.yevs]

for a while, i had assumed that a substance's reactivity depends on its electrongativity... but i'm starting to find some faults with this...

 

for example, what is more reactive, copper or hydrogen? copper has lower electronegativity but is lower in the reactivity series. And if hydrogen is more reactive, shouldn't copper chloride or copper sulfate be a stronger lewis acid then hcl or h2so4, respectively?

 

and what's more reactive, chlorine or oxygen? oxygen has higher electronegativity, but say preheated aluminum foil will burn in chlorine but usually not in oxygen...

 

and for example sulfur, iodine, and carbon all have similar electronegativity, but I2 will react with aluminum scraps, while if anything, carbon and sulfur burn.

 

(of course for the chlorine and iodine, how close they are to the stability of a full shell might explain their reactivity)

[CaptainPanic]

I think you're well on your way to understanding at least the reactions, but perhaps not yet some definitions.

 

What you're mixing up (I think) is:

reactivity of 1 single component

reactivity of 1 single component in the presence of another component (so actually the reactivity of the mixture)

 

I think that these are two different things.

 

And to be honest, I don't think that the reactivity of a single component is a very useful definition, unless you can identify a reaction that is likely to take place. I've never used the definitions of reactivity so much.

A better description of the readiness of some component or mixture to react is the "Gibbs energy of reaction". But perhaps that goes a bit far for this moment. The message that I want to get across is that this Gibbs energy of reaction looks at the difference in energy levels of the reactants and the products. This difference is what causes the reaction to take place.

 

Please note that this is still a bit of a simplification. I guess I should refer to a thermodynamics book for a complete and thorough explanation.

[max.yevs]

yeah, thanks, so far i've just been trying to determine whats more reactive just by using a thermochemical calculator , chemix...

 

its just i had kind of assumed that reactivity is a direct reflectment on electronegativity... which works most of the time but not always