How to Tell If a Compound Is Ionic or Covalent

Table salt is an example of an ionic compound.

When two atoms are combined in a compound, there is a bond between the atoms. This bond can be between two atoms of the same element or two different elements. Covalent bonds occur when pairs of electrons are shared by atoms, while ionic bonds only share a single electron. Covalent bonds require more energy to break than ionic bonds, which means that ionic bonds tend to be more soluble, as demonstrated by how table salt (sodium chloride) dissolves easily in water.

Instructions

1. Observe the shape of the compound. Substances with ionic bonds do not have a finite shape, while covalent bonds have distinct and definitive shapes.

2. Heat the compound until it boils. Covalent bonds have relatively low boiling points, while ionic bonds have higher boiling points. This is why many covalent substances are liquids or gases at room temperature.

3. Place the compound in water. If water dissolves the compound, then it is ionic, since ionic bonds dissolve in polar substances such as water. If it does not dissolve in water, then the compound is covalent. Similarly, ionic compounds do not easily dissolve in nonpolar substances.

4. Determine what substances are bonded together. Ionic bonds are made between a nonmetal and a metal, such as silver ions and nitrate ions bonding to form silver nitrate. Covalent bonds are formed between two nonmetals, such as when carbon and oxygen come together to form carbon monoxide.

References

• Diffen: Covalent Bonds vs Ionic Bonds: Difference and Comparison
• Washington University in Saint Louis: Compounds of Great Ionic Character
• Washington University in Saint Louis: Compounds of Great Covalent Character