[grhino]

Admittedly not a biochemist, but I believe sodium and chlorine lose most of their activity when they give up or accept that electron, respectively, to fill their octet. From a biochemistry perspective, they are mostly used as convenient ions to generate voltage differences or activate structural changes in enzymes.The chemical difference between sodium ions and potassium ions are relevant at times, free sodium ions or chloride ions are not nearly as reactive as their neutral complements. It's also very unlikely that sodium ions or chloride ions would spontaneously transform into their neutral complements.