sodium element is likely to have the highest thermal conductivity
<span>If energy is released, the reaction is exothermic. If energy is absorbed, the reaction is endothermic. Since heat is being absorbed in this reaction (to break down H2O into H2 and O), the reaction is endothermic.</span>
Not sure what you are asking. I have two possible answers though...
It could either be more negatively charged, or valence electrons.
The more away from the nucleus a electron is, the more negatively charged it is.
The electrons on the outermost electron shell is valence electrons.
Again, I don't know what you were asking, but one of these answers may be correct.