Net ionic equation calculator

A net ionic equation shows only the chemical species that actually change during a reaction in solution. Starting from the aqueous ions written on each side of a full ionic equation, this calculator cancels spectator ions that appear identically among reactants and products and returns the remaining net ionic equation as a single string. Precipitation, neutralization, and many redox-in-solution drills all reduce to that cancellation once every strong electrolyte is already split into ions. Students, tutors, and exam-prep scripts need a deterministic answer that fails loudly when a listed ion has an invalid charge format instead of silently dropping the token.

What a net ionic equation is and how spectator ions cancel

In aqueous chemistry the molecular equation writes intact compounds, the full ionic equation splits every strong electrolyte into the ions that actually exist in water, and the net ionic equation keeps only the species whose formulas or charges change. Ions that sit on both sides in equal amount are spectators: they balance charge and keep the solution electrically neutral, but they do not participate in forming a precipitate, a weak electrolyte, a gas, or a redox product. Canceling them is a multiset subtraction, not a chemical opinion.

If the left side lists Ag+, NO3-, Na+, and Cl-, and the right side lists AgCl(s), Na+, and NO3-, then Na+ and NO3- cancel one-for-one and the net ionic equation is Ag+(aq) + Cl-(aq) → AgCl(s). Coefficients matter: two chloride ions on the left cancel two chloride ions on the right, and a leftover coefficient stays on the net side. Molecular species such as AgCl(s), H2O(l), and CO2(g) are not spectators unless the same formula and state appear on both sides; they remain so the net equation stays complete.

The algorithm never invents a solid you did not list, never applies solubility rules, and never reorders atoms inside a formula. It only reads the lists you send, matches identical aqueous ions by formula and integer charge, and writes the remainder with a single arrow.

Input contract, accepted charge formats, and error behaviour

Each item is an object with a required ion string and an optional positive integer coefficient that defaults to one. You may also send a plain string in place of the object; a leading coefficient glued to the formula, such as 2Cl-, is honoured. Every aqueous ion must carry a valid charge format.

Accepted shapes include a trailing sign for magnitude one (Na+, Cl-, NH4+, NO3-, OH-), a magnitude from one through eight then a sign after a letter or bracket for simple ions (Ca2+, Al3+, Fe2+, O2-, [Fe(CN)6]4-), a caret form for polyatomic ions whose formula already ends in a digit (SO4^2-, PO4^3-, CO3^-2), a parenthetical charge (SO4(2-), Fe(3+)), and Unicode superscripts such as Na⁺ or SO₄²⁻ which are folded to ASCII before parsing. Optional (aq) on an ion is accepted and normalised.

Molecular species must carry a non-aqueous state in parentheses: (s), (l), or (g). Missing arrays, empty arrays, more than forty species on one side, coefficients outside one through fifty, and non-finite junk fail the same way and are not billed. Display writes magnitude-one charges as a trailing sign, writes Ca2+ without a caret, and writes SO4^2- with a caret so a formula that ends in a digit never collides with the charge.