B.Mg(OH)2 (the active ingredient in milk of magnesia)
Zn⁰ ----> Zn⁺² + 2e⁻ - oxidation
Hg⁺² + 2e⁻ ----> Hg⁰ - reduction
Zn loses 2 moles of electrons , and Hg gains 2 mole of electrons.
So, number of moles of electrons gained and lost during reaction is equal.
Well, TECHNICALLY, the periodic table is "based" upon a whole myriad of characteristics. But if you're talking about the consecutive arrangement of elements...it would be B, the atomic number.