Classify Compounds as Ionic or Covalent

How to Classify Ionic vs. Covalent Compounds

It is often challenging to determine whether a compound is covalent or ionic. However, the formula or name of a compound contains information that can be used to classify it. The following guidelines show how the two classes of compounds are similar and how they differ.

Note: When forming compounds, metalloids act more like nonmetals than metals. Whenever nonmetals are mentioned here, that includes metalloids as well.

🔗 Covalent Compounds

  • Contain only nonmetals (and/or metalloids)
  • Do not contain polyatomic ions (such as the ammonium ion)
  • Are named using prefixes to indicate the number of each element in a formula

⚡ Ionic Compounds

  • Contain metals and nonmetals, or contain polyatomic ions
  • Are never named using prefixes
  • Are sometimes named with the cation charge in Roman numerals within parentheses

Reference: Periodic Table

Use this table to identify metals, metalloids, and nonmetals.

Periodic Table of Elements

Reference: Common Polyatomic Ions

It is important to recognize these common polyatomic ions.

Names and Formulas of Common Polyatomic Ions