Why sodium reacts with water

Sodium reacts violently with water because it is much more active than hydrogen. Although water is covalent, not ionic, it is helpful sometimes to consider water to be [H+][OH-], since after all hydrogen has a slight excess of positive charge. Sodium is very stable in a positive oxidation state in comparison to neutral sodium atoms; the difference is much greater than that for hydrogen. Therefore, a redox reaction between H+ and Na to give H(2) and Na+ is very energetically favorable. So much energy is released that the hydrogen gas released can burn.