The sodium atom and the sodium ion are obviously very closely related but have some very different properties. Both have 11 protons in their nuclei but the sodium atom has 11 electrons while the sodium ion has only 10 electrons. Sodium is a group 1 alkali metal and as such readily loses the eletctron in its outermost valence shell (in this case 3s1) to form a cation with a plus one charge. The sodium atom is a neutral compound and is actually a soft, white colored metal. It is extremely reactive with water and produces extreme heat and hydrogen gas so the reaction is explosive. The sodium ion, on the other hand, is an ion and outside of an aqueous solution must be paired with an anion like chloride (Cl-). The sodium ion goes readily into water with no dangerous release of energy or heat. In water, the sodium ion acts as an electrolyte to help the solution conduct electricity.