Acronyms that contain the term spectator ion 

Spectator ion

A spectator ion is an ion that exists as a reactant and a product in a chemical equation. Spectator ions can, for example, be observed in the reaction of aqueous solutions of sodium carbonate and copper sulfate but does not affect the equilibrium: 2Na⁺ + CO₃ 2− + Cu²⁺ + SO₄2− → 2Na⁺ + SO₄2− + CuCO3 The Na⁺ and SO₄2− ions are spectator ions since they remain unchanged on both sides of the equation. They simply "watch" the other ions react, hence the name. They are present in total ionic equations to balance the charges of the ions. Whereas the Cu²⁺ and CO₃²⁻ ions combine to form a precipitate of solid CuCO₃. In reaction stoichiometry, spectator ions are removed from a complete ionic equation to form a net ionic equation. For the above example this yields: So: 2Na⁺ + CO₃2− + Cu²⁺ + SO₄2− → 2Na⁺ + SO₄2− + CuCO₃ ₍ₛ₎ = CO₃2− + Cu²⁺ → CuCO₃ ₍ₛ₎ Spectator ions concentration only affect the Debye length. In contrast, Potential Determining Ions, whose concentrations affect surface potential as well the Debye length.

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