Weak electrolytes are primarily molecules when dissolved in a solution. This is because a weak electrolyte produces very few ions when placed in a solution, and it only partially dissociates.
Weak electrolyte compounds are typically comprised of polar covalent bonds. These types of bonds are formed when two atoms share electrons evenly, rather than gaining or losing an electron as occurs in ionic bonding. Covalent bonds usually form weak acids or bases, meaning they have a pH value that is close to neutral (7). The strongest and most common covalent bond is H2O (water). Other examples include ammonia and hydrogen fluoride.
Strong acids or bases, such as hydrochloric acid or magnesium hydroxide, will be ions rather than molecules when placed in a solution, giving them a positive or negative charge.