Well, a few of the 3rd period elements do react with water. Sodium definitely does. Magnesium reacts with gaseous water, and chlorine reacts mildly with water to form HCl and HOCl. I don't know of any reactions between sulfur or phosphorus and water. (In fact, white phosphorus is actually stored in water). Whether or not they form acids also depends on where they are on the periodic table. The elements to the left of the table will generally form bases with water, and those on the right will generally form acids. (Sodium reacts with water to produce NaOH which is a base, and Mg reacts with steam to form Mg(OH)2
which is a base. As I had mentioned earlier, chlorine produces an acid when reacting with water). Aluminum forms a protective layer of aluminum oxide on its surface which prevents its reaction with water, but I do know that aluminum hydroxide is somewhat amphoteric. (That is, it sometimes acts as a base and sometimes acts as an acid). The oxides of the elements are generally what determines whether or not its a base or acid in water. Sodium, Magnesium, and very slightly Aluminum oxides will form bases, while Sulfur, chlorine, and phosphorus oxides form acids. I really have no clue about silicon. I'm fairly certain that all silicon oxides are completely non-reactive with water. If they were, sand would not exist! (Silicon oxides are generally pretty inert).
As for the structure, I'll have to get back to you later on that one.