As we begin to talk about the solubility rules, we first have to familiarize ourselves with the term solubility. Now, solubility is just a chemical property that deals with the ability of a solute to become dissolved in a solvent. Remember, solutes get dissolved in solvents to create solutions. Now, with the term solubility, we're introduced to two other terms: soluble versus insoluble.
Now we're gonna say soluble refers to a solute that could be dissolved into aqueous ions when placed in a solvent. So here we have aluminum bromide solid. We're gonna throw it into water. We're saying that it's soluble, so it's gonna break up into its ions. Aluminum bromide possesses one aluminum, so it's gonna break up into one aluminum ion. Aluminum is in group 3, so its charge is 3+. It is an ion. And when you have an ion within water, water actually surrounds the ion. And in that state, we call it aqueous.
Okay, so a soluble ionic solute breaks up into an aqueous ion. But that's not the only ion that we have. What else do we have within this formula? Aluminum bromide has three bromines in it. So we have three Br- ions. Since it's an ion as well, it's aqueous within the solution. So here we break up into one aluminum ion (Al3+) and three bromide ions (Br-).
Now, if you're insoluble, it refers to a salt that cannot be dissolved when placed in a solvent. Here we have silver bromide. Silver bromide, we're told, is insoluble. So even when I throw it into water, it will not break up into ions and stays together. So it doesn't change in any way. And that's how we are able to distinguish soluble versus insoluble: soluble compounds break up into ions, aqueous ions, while insoluble ones tend not to.