In a net ionic equation, what is excluded from the formula?

In a net ionic equation, spectator ions are excluded from the formula. The purpose of a net ionic equation is to show only the species that undergo a change during the reaction, typically ions or molecules that participate in forming products, such as precipitates, gases, or weak electrolytes. Spectator ions, on the other hand, are ions that do not participate in the actual chemical change and remain unchanged throughout the reaction process. By removing these spectator ions, the net ionic equation provides a clearer representation of the chemical processes occurring in the solution.

The clarity provided by excluding spectator ions is vital for understanding the actual reactants and products of the reaction. This distinction is particularly important in full ionic equations, where both the reacting species and spectator ions are included. Removing the spectator ions to formulate a net ionic equation emphasizes the core chemical changes that are relevant to the reaction at hand.