In the blockbuster film hit Back to the Future, which came out 30 years ago, and its sequels, this, 2015, is the future - the year Marty McFly and Doc Brown zoomed off to visit in their souped-up flying DeLorean.
Metallic bonding in magnesium. If you work through the same argument with magnesium, you end up with stronger bonds and so a higher melting point. Magnesium has the outer electronic structure 3s 2. Both of these electrons become delocalised, so the sea has twice the electron density as it does in sodium. The remaining ions also have twice the charge (if you are going to use this particular view of the metal bond) and so there will be more attraction between ions and sea.
Magnesium is more reactive than iron. So Magnesium loses electrons in preference to iron. Magnesium reacts with the oxygen in the air to form Magnesium Oxide, and the iron remains protected, because it has magnesium attached to it. Magnesium is oxidised as it dissolves. Iron ions are reduced to iron atoms. The iron ions take the electrons given out by magnesium, and form iron metal.