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Chemical Name Calculator

Ready to calculate
37 Cations · 35 Anions.
Auto Charge Balance.
Roman Numerals (II, III, IV).
100% Free.
No Data Stored.

How it Works

01Pick the Mode

Search by chemical formula (K⁺, CrO₄²⁻) or by name (Potassium, Chromate)

02Choose Cation & Anion

37 cations · 35 anions — covers the full IUPAC ion library

03Auto Charge Balance

Subscripts derived from LCM of charges — guaranteed neutral compound

04Get Name + Formula

IUPAC name with Roman numerals for variable-charge metals — copy-ready

About the Chemical Name Calculator

The Chemical Name Calculator builds the correctly charge-balanced ionic formula and the matching IUPAC compound name from any cation–anion pair. Pick from 37 cations (including every variable-charge transition metal — Iron(II)/Iron(III), Copper(I)/Copper(II), Manganese(II/III/IV), and more) and 35 anions (monatomic -ide ions plus the full IUPAC polyatomic library — sulfate, chromate, permanganate, dichromate, carbonate, nitrate, phosphate, and others). Choose your input mode — by formula if you know symbols and charges, by name if you prefer English. The tool handles both directions equivalently.


Behind the scenes, the calculator computes the least common multiple of cation and anion charges to determine subscripts, wraps polyatomic anions in parentheses when their subscript exceeds 1 (so iron(III) phosphate becomes FePO₄ but calcium phosphate becomes Ca₃(PO₄)₂), and emits Roman numerals only for variable-charge cations — exactly as required by IUPAC inorganic nomenclature. A reference library of 25+ common compounds adds context (table salt, milk of magnesia, slaked lime, gypsum, etc.) when your selection matches a well-known substance.

How the Calculator Works

Pick the search mode: formula (K⁺, CrO₄²⁻) or name (Potassium, Chromate). Both modes work identically — the toggle just controls how the dropdowns are labeled.
Choose a cation from the 37-ion library: Group 1 (H, Li, Na, K, Rb, Cs, Ag), Group 2 (Be, Mg, Ca, Sr, Ba, Zn, Cd), Group 13 (Al), the polyatomic NH₄⁺, and the variable-charge transition metals (Fe, Cu, Cr, Mn, Co, Ni, Sn, Pb, Au, Hg) — each at their valid oxidation states.
Choose an anion from the 35-ion library: monatomic -ide ions (H⁻, F⁻, Cl⁻, Br⁻, I⁻, O²⁻, S²⁻, N³⁻, P³⁻, etc.) and polyatomic ions (OH⁻, NO₃⁻, SO₄²⁻, CO₃²⁻, PO₄³⁻, MnO₄⁻, CrO₄²⁻, Cr₂O₇²⁻, ClO/ClO₂/ClO₃/ClO₄⁻, and more).
Press Calculate. The tool computes subscripts via LCM(cation charge, anion charge), wraps polyatomic groups in parentheses when needed, and assembles the formula in correct ionic-compound order (cation first, anion second).
Read the IUPAC name. Cation name + anion name; for variable-charge metals, a Roman numeral indicates the cation's oxidation state. The calculator also shows the charge-balance worksheet and (when applicable) a reference note about the compound's common uses.

The Math Behind the Calculator

The calculator runs three computations in sequence:


1. Charge balance: for cation charge x and anion charge y, find the smallest subscripts (a, b) such that a·x − b·y = 0. The unique solution is a = y/gcd(x,y) and b = x/gcd(x,y) — derived from the least common multiple of x and y.


2. Formula assembly: write the cation symbol (with subscript if a > 1), then the anion. If the anion is polyatomic and b > 1, wrap it in parentheses: Ca(NO₃)₂, Al₂(SO₄)₃. Monatomic anions never need parentheses.


3. IUPAC name: cation name + anion name. For variable-charge metals (Fe, Cu, Cr, Mn, Co, Sn, Pb, Au, Hg), append the oxidation state in Roman numerals — Iron(II), Copper(II), Lead(IV). For fixed-charge metals (Group 1, 2, 13, plus Ag, Zn, Cd), no Roman numeral is used — sodium chloride, not sodium(I) chloride.

Real-World Example

Worked Examples

Three worked examples covering the algorithm's edge cases:

Cation Anion LCM Formula IUPAC Name
K⁺ (+1)CrO₄²⁻ (−2)2K₂CrO₄Potassium Chromate
Ca²⁺ (+2)PO₄³⁻ (−3)6Ca₃(PO₄)₂Calcium Phosphate
Fe³⁺ (+3)O²⁻ (−2)6Fe₂O₃Iron(III) Oxide (rust)

Notice how the polyatomic phosphate gets parentheses when its subscript exceeds 1 (Ca₃(PO₄)₂), but the monatomic oxide does not (Fe₂O₃). And iron requires the Roman numeral III because iron also forms Fe²⁺ — without it, the name is ambiguous.

Who Uses It

1
🧪 Chemistry Students: Verify ionic compound formulas and IUPAC names for homework, lab reports, and exam prep — no more arguing with TAs about whether NaCl needs a Roman numeral (it doesn't; sodium is fixed +1).
2
👨‍🏫 Chemistry Teachers: Generate worked examples on the fly during lecture, with the charge-balance reasoning visible to students.
3
🏫 General Chemistry Courses: Drill ionic naming — the most-tested topic in first-semester gen chem, and the source of the most lost points on midterms.
4
🔬 Lab Technicians: Quick verification when transcribing reagent labels — catch typos before they make it into a procedure.
5
📚 SAT Subject / AP Chemistry: The naming-and-formula questions are about 8% of the AP Chemistry exam. This calculator is a fast self-check tool.
6
👨‍🎓 Chemistry Olympiad / Quiz Bowl: Reference for the trickier compounds (mercury(I) chloride, lead(IV) sulfate) where most students stumble.

Technical Reference

The naming and charge-balance algorithm follows IUPAC's 2005 recommendations on inorganic nomenclature (Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005, Connelly et al., RSC Publishing). Key conventions:

  • Cation written first, anion second.
  • Stock notation (Roman numerals) for variable-charge metals — preferred over the older -ic / -ous Latin-stem system (cupric, cuprous).
  • Polyatomic groups parenthesized only when the subscript exceeds 1.
  • Subscripts derived from charge balance; no leading "1" subscript ever appears.
  • Greek prefixes (mono-, di-, tri-) are NOT used for ionic compounds — that convention is reserved for binary covalent compounds.

The 37-cation × 35-anion library covers the standard introductory chemistry curriculum. For more obscure species — peroxides (O₂²⁻), superoxides (O₂⁻), hydrosulfides (HS⁻), or organometallic cations — consult a reference table.

Final Thoughts

Ionic compound naming is the foundation of inorganic chemistry — a skill that gen chem students are expected to master in the first six weeks and that resurfaces in every analytical, environmental, and biochemistry course thereafter. The two failure modes are subscript-balancing arithmetic and forgetting Roman numerals on variable-charge metals. The ToolsACE Chemical Name Calculator removes both, every time, with the math transparent so you can see exactly why Iron(III) phosphate is FePO₄ and Calcium phosphate is Ca₃(PO₄)₂. Use it as a homework verifier, a study aid, or a reference card you wish you'd had during the periodic-table memorization phase.

Frequently Asked Questions

What's the difference between formula mode and name mode?
Just the dropdown labels. Formula mode shows ions as symbols (K⁺, CrO₄²⁻); name mode shows them in English (Potassium, Chromate). The output and underlying calculation are identical — pick whichever feels more natural.
How does the calculator decide on subscripts?
It computes the least common multiple (LCM) of the cation charge and anion charge, then divides each by its respective charge to get the subscripts. For Ca²⁺ + PO₄³⁻: LCM(2,3) = 6, so cation subscript = 6/2 = 3 and anion subscript = 6/3 = 2 → Ca₃(PO₄)₂.
When does a Roman numeral appear in the name?
Only for variable-charge cations — transition metals (Fe, Cu, Cr, Mn, Co, Ni, Sn, Pb, Au, Hg) plus a few others — that can adopt multiple oxidation states. Sodium is always +1, so 'sodium chloride' needs no numeral. Iron can be +2 or +3, so 'iron chloride' is ambiguous — it must be specified as iron(II) chloride or iron(III) chloride.
Why are some anions wrapped in parentheses in the formula?
Polyatomic anions get parentheses when their subscript is greater than 1, to preserve the polyatomic group's identity. Ca₃(PO₄)₂ is unambiguous (3 calcium ions, 2 phosphate groups). Without parentheses, Ca₃PO₄₂ would be misread as 'Ca₃P O₄₂' — gibberish. Monatomic anions don't need parentheses (Fe₂O₃, never Fe₂(O)₃).
What's the difference between -ide, -ate, and -ite endings?
-ide is for monatomic anions: chloride (Cl⁻), oxide (O²⁻), nitride (N³⁻). -ate is for the higher-oxygen oxoanion in a pair: sulfate (SO₄²⁻), nitrate (NO₃⁻), phosphate (PO₄³⁻). -ite is for the lower-oxygen oxoanion: sulfite (SO₃²⁻), nitrite (NO₂⁻), phosphite (PO₃³⁻). The calculator uses the standard library names.
Does it handle hypochlorite, chlorate, and perchlorate?
Yes — the full chlorine-oxoanion ladder: ClO⁻ (hypochlorite), ClO₂⁻ (chlorite), ClO₃⁻ (chlorate), ClO₄⁻ (perchlorate). Same prefixes apply to bromine and iodine analogs in extended IUPAC nomenclature, though those aren't included since they're rarely encountered.
Why isn't ammonia (NH₃) in the calculator?
Ammonia is a covalent (molecular) compound, not an ionic compound. This calculator builds salts — ionic compounds with a clear cation and anion. Covalent compounds use a different naming system (Greek prefixes: dinitrogen tetroxide, sulfur hexafluoride). Ammonium (NH₄⁺), the protonated cation, IS in the calculator.
Can I use this for hydrates like CuSO₄·5H₂O?
Not directly — the calculator outputs the anhydrous formula (CuSO₄, copper(II) sulfate). Hydrate notation appends '·n H₂O' (e.g., CuSO₄·5H₂O = copper(II) sulfate pentahydrate). The base compound is what the calculator returns; you can add the hydrate suffix manually if relevant.
What about acids like HCl and H₂SO₄?
The calculator returns the binary name (hydrogen chloride for HCl, hydrogen sulfate is more nuanced) — which is technically correct for the anhydrous gas form. The aqueous-acid names (hydrochloric acid, sulfuric acid) follow different conventions: -ide → -ic acid, -ate → -ic acid, -ite → -ous acid.
Why does Hg₂²⁺ (mercury(I)) appear as a single Hg⁺?
For simplicity. Mercury(I) actually exists as a dimeric Hg₂²⁺ cation in real chemistry — calomel is Hg₂Cl₂, not HgCl. The calculator currently treats it as Hg⁺ for ease of subscripting; advanced inorganic students should know the dimer is the real species.
How do I know if a metal needs a Roman numeral?
If the metal is in Group 1 (alkali), Group 2 (alkaline earth), Group 13 (Al), or is Ag/Zn/Cd — fixed charge, no numeral. Everything else (transition metals, p-block metals like Pb/Sn) — variable charge, use Roman numerals. The calculator handles this automatically.
Can I share the calculator's output?
Yes — every result panel has Copy buttons for the formula and the name, plus Share and Download Report buttons in the footer. The downloadable PDF includes the inputs, charge-balance worksheet, and IUPAC name.
Is my data private?
Yes. Everything runs in your browser. Your selections and results are not stored, logged, or transmitted to any server.

Author Spotlight

The ToolsACE Team - ToolsACE.io Team

The ToolsACE Team

Our chemistry tools team implements the IUPAC ionic-compound naming convention and charge-balance algorithm. The tool covers 37 common cations (including all variable-charge transition metals) and 35 anions (monatomic and polyatomic). Subscripts are derived from the least common multiple of cation and anion charges; Roman numerals are inserted automatically for variable-charge metals like Iron(II) vs Iron(III).

IUPAC Inorganic NomenclatureIonic Compound NamingSoftware Engineering Team

Disclaimer

The calculator covers ionic (salt) compounds. Covalent / molecular compounds (e.g. CO₂, H₂O, NH₃) follow different naming rules and are not included. For acids in aqueous solution, the binary-compound name returned is correct for the gaseous/anhydrous form; the aqueous-acid form (hydrochloric acid, sulfuric acid) follows separate IUPAC conventions.