Spectator Ion Posted on 21st December 20157th May 2021 by ThePD (The Project Definition) A Spectator Ion is an ion that exists as a reactant and a product in a chemical equation that does not affect equilibrium. Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in Science and tagged chemistry. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.