Sodium chloride crystal and conceptual ion tokens on a mint laboratory surface. Original AI-generated editorial artwork produced for GreenCalc.
Calcium chloride is CaCl₂ because each calcium ion has charge +2 and each chloride ion has charge −1. Two chloride ions balance one calcium ion. The formula is a charge-balanced ratio, not a drawing of a discrete calcium chloride molecule.
Begin with the ions
The Chemical Name Calculator lets you choose from a defined list of cations and anions. It writes the cation name first, the anion name second, and reduces the ion ratio to the smallest whole numbers that give zero total charge.
For ions of charges +a and −b, the cation count is b/gcd(a,b), and the anion count is a/gcd(a,b). Magnesium oxide illustrates why reduction matters: +2 and −2 balance in a 1:1 ratio, giving MgO rather than Mg₂O₂.
Roman numerals identify the metal's oxidation state
Iron(II) chloride and iron(III) chloride are different compounds. Fe²⁺ requires two chloride ions, giving FeCl₂. Fe³⁺ requires three, giving FeCl₃. The Roman numeral describes the iron oxidation state in these names; it is not a count of iron atoms.
Likewise, copper(I) oxide is Cu₂O, while copper(II) oxide is CuO. Selecting the metal symbol without its charge would leave the intended compound ambiguous. The calculator keeps those cation choices separate.
Keep a polyatomic ion together
Calcium nitrate combines Ca²⁺ and NO₃⁻. Two nitrate ions are required, so the formula is Ca(NO₃)₂. The outside subscript multiplies the whole parenthesised group: one calcium, two nitrogen atoms and six oxygen atoms.
Ammonium sulfate works in the other direction. Two NH₄⁺ ions balance one SO₄²⁻ ion, giving (NH₄)₂SO₄. A polyatomic group used once does not need parentheses in these simple formulas. Aluminium sulfate, Al₂(SO₄)₃, combines a 2:3 ion ratio with parentheses around repeated sulfate.
What this naming tool covers
This is a supported-ion formula builder for common ionic examples. It does not parse arbitrary organic structures, infer stereochemistry, name coordination complexes, or add hydrate water. A charge-balanced pair is also not proof of a stable, isolable compound: chemical feasibility requires more information.
Names and formulas depend on the actual species. Do not use an ionic naming routine to label a covalent compound merely because its formula contains familiar elements.
Connect names with atomic structure
The Atom Calculator shows how ionic charge relates to proton and electron counts. The particle-count guide explains why forming a cation changes the electron count while leaving the element identity intact. These tools and the naming calculator are linked from the Chemistry category.
By GreenCalc · Updated 2026-10-21
Frequently asked questions
Does this tool name every chemical compound?
No. It builds names and formulas from its supported list of common cations and anions.
When are parentheses used?
A repeated polyatomic ion is enclosed in parentheses before its group subscript.