How do I name compounds?

Nomenclature for Naming Ionic Compounds 💡

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Rules

• Keep the name of the cation (the ion that loses valence electrons). This is usually the first part of the chemical formula.
• Cut off the end of the anion's name and add the -ide suffix.
• If the anion is a polyatomic ion, don't change the name.

Examples of Naming Ionic Compounds

NaCl - sodium chloride

Al₂Se₃ - aluminum selenide

LiH - lithium hydride

NH₄NO₃ - ammonium nitrate

CaCO₃ - calcium carbonate

For cations with multiple charges:

• Sometimes, cations can have multiple charges. For example, iron can have a +2 or a +3 charge. Most transition metals will have multiple charges, besides some exceptions like Zn²⁺ and Ag⁺.
• If a cation can have different charges, include its charge in the compound after the actual name of the cation. Write it in roman numerals between parentheses.
• To determine the Roman numeral, use charge balance: the total positive charge must equal the total negative charge in the neutral ionic compound.
• Do not use Roman numerals for metals with fixed charges, such as Group 1 metals (+1), Group 2 metals (+2), Al³⁺, Zn²⁺, Ag⁺, and commonly Cd²⁺.
• Here are a few examples:

VO - vanadium(II) oxide

FeCl₃ - iron(III) chloride

Cu₃P₂ - copper(II) phosphide

MnSO₄ - manganese(II) sulfate

Nomenclature for Naming Molecular Compounds 🔬

Rules:

Use these prefixes for binary molecular compounds, which are formed between two nonmetals.

• Keep the name of the first element the same.
• Cut off the end of the second element and add the -ide suffix.
• Now, add the correct prefix to both elements based on their subscripts:

1: mono-

2: di-

3: tri-

4: tetra-

5: penta-

6: hexa-

7: hepta-

8: octo-

9: nona-

10: deca-

• If there's only one atom of the first element, you don't need the mono- prefix. For example, NO₂ is nitrogen dioxide, not mononitrogen dioxide.

Examples for Naming Molecular Compounds

P₃O₅ - triphosphorus pentoxide

N₂O₄ - dinitrogen tetroxide

CO₂ - carbon dioxide

SiO - silicon monoxide

Naming Acids 🧪

• If a formula begins with H and is aqueous, it is often named as an acid.
• Binary acids: hydro- + anion stem + -ic acid. Example: HCl(aq) = hydrochloric acid.
• Oxyacids: anions ending in -ate become -ic acid, and anions ending in -ite become -ous acid. Examples: HNO₃(aq) = nitric acid, HNO₂(aq) = nitrous acid.
• Without (aq), compounds such as HCl can be named as molecular substances instead: hydrogen chloride.