Identify if a compound is covalent or ionic

  1. You will need to know the periodic table
  2. You must be able to identify the non-metals, metals, and transition elements in the periodic table
  3. You must be able to categorize a compound as ionic or covalent formed from elements based on their location within the periodic table
  4. If the substance is an ionic compound, follow the rules for ionic compounds
  5. If the substance is a covalent compound, follow the rules for covalent compounds

You can download the following flowchart to serve as a guide for naming compounds.


The periodic table


It’s important that you can identify if a compound is a covalent compound or an ionic compound by looking at the periodic table. The periodic table below shows the metals, non-metals and metalloids. Use it to determine if a compound is ionic or covalent.

Periodic table



Covalent compounds are generally formed between non-metals.

Eg. Water (H2O), carbon monoxide (CO), hydrochloric acid (HCl)

covalent compound non-metal + non-metal

Ionic compounds are generally formed between a metal and a non-metal

Eg. Sodium chloride (NaCl),  potassium fluoride (KF),  magnesium oxide (MgO)

ionic compound - metal + non-metal


Metalloids (semi-metals)

Metalloids: Boron, silicon, germanium, arsenic, antimony, and tellurium.

Metalloids generally form covalent bonds with non-metals. But sometimes, they form ionic compounds with other elements.

metalloid + non-metal

SiO₂, silicon dioxide, is a covalent compound.

As₂O₃, arsenic(III) oxide, is an ionic compound.


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2. Learn the rules for covalent compounds