[Miffymycat]

Carbon is higher in the electrochemical series than hydrogen, which indicates it is more electropositive, but Pauling values show carbon as more electronegative - 2.55 vs 2.2!!?

Any reason / explanation for the apparent contradiction? Tried looking for an Eo value for C (should be more negative then -0.76V) but no joy ...

Come to that, Li is less reactive than K, but has a greater Eo ...
 
Thanks in advance for any replies

[isha2ubt]

hello,
I can not answer about carbon but can tell about the Li and K.!!
the electrochemical series is all about the voltage that is produced when reaction occurs.

"Lithium "pushes away" its electron with a greater force than any other metal, but it does not give it away fast. So lithium would have the most voltage in a standard electrode potential chart, but other alkali metals would be more reactive on the activity series."
I found it somewhere written.May be this explains.I think reactivity series is different from electrochemical series else why two series would have been necessary?

[Enthalpy]

You can forget "pushes away" and "fast". Any cation attracts electrons.

[Miffymycat]

Thank you.  Yes I have now discovered that Li indeed has the largest negative delta G for its reaction with water and hence the largest exotherm, but is the slowest to react due the highest activation energy (first ionisation energy highest).  Its all about kinetics versus thermodynamics and the distinction is between reactivity as reaction "power" (ie J released or gained/s) vs reaction energy change (total J exotherm or endotherm).

Electronegativity and Electrode potentials are fundamentally different in concept and nature and any slight correlation is more by chance than cause.  The former is based on differences between respective element bond strengths or ionisation energies whereas the latter is based on the free energy change for the reduction process Oxidised form + e -> Reduced form ... as you can see I have since been able to answer my own question!   

[Enthalpy]

Ionization energy is for individual atoms, which you may have in gaseous metal, but not in the solid which is a molecule. And in a solution, the electrons go to an other molecule, not to vacuum. So ionization energy does not represent what happens with solid lithium in an electrolyte.