If you are given a formula how do you know which elements to use for the net ionic equation
Hey! So for net ionic equations, you start off with reactants and must complete the reaction with the products. Some problems will already give you the products. Before achieving the net ionic equation, there are a couple of steps. You must first have the complete balanced chemical equation and you must know solubility rules. Solubility rules are important because you must be able to identify whether one of the products is is insoluble (creating a solid) or not. If a solid is formed, that is what you will be using for your ionic equation.
Next comes the total ionic equation. Here, everything that is aqueous will split up into separate ions. Anything that is solid will stay together and not dissociate. Remember that solids do not dissociate. So here, you must cancel out the spectator ions. Spectator ions are those that won't be used in your net ionic. You cancel them out because they will be both on the reactant and product side. Everything will cancel out and whatever is left will be part of your net ionic equation. In the end, you will have something like : 2A + B --> A2B (s) . For more information, you can check Jules's videos on net ionic equation. Hope this helped!