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:

• Check out this Resonance and Formal Charges Study Guide to learn more
• 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 help you figure out the charge of the cation, keep in mind that the total charge of the cation(s) should be the same magnitude as the total charge of the anion(s). Pay attention to subscripts!
• 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:

• 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

S₂O₆ - disulfur hexoxide

CO₂ - carbon dioxide

SiO - silicon monoxide