[orgopete]

I mean why is it that sodium and water react, but Ethanol and mercury don't? My question is more like, based on what facts do you say that?

Sodium, as other alkali metals has one more electron than needed for it to havena completed shell. Consequently, that electron is held at a greater distance due to the repulsion of the inner electrons. Simple Coulombic attraction results in the protons of water or ethanol reacting with those electrons. The net result is formation of H2 and NaOH. The electrons of mercury are held more tightly so a simple protonation by water or ethanol does not occur. However, if mercury has lost some of its electrons, it's nuclear charge is sufficient for it to attract addition electrons from other atoms. This is the driving force for mercury salt reactions with alkenes and alkynes. Since sodium readily looses it's valence electrons, it has only a weak attraction to the electrons of other atoms.