The trend in reactivity we have already discussed and the reasons behind it parallel those for the alkali metals as well.

These vertical trends give us some indication of the effects of increasing shielding as you move from top to bottom in a family. Comparing the reactivity with water for the sequence Na, Mg, Al indicates the difference in reactivity as a result of decreasing shielding. The reaction with sodium is vigorous. Magnesium reacts only with very hot water (or steam) and must be very clean. Under ordinary conditions, aluminum does not appear to react with water at all. How does shielding explain this?