Overview
This lecture explains the different types of chemical bonds—ionic, covalent (polar and nonpolar)—and how electronegativity differences determine bond type.
Types of Chemical Bonds
- Molecules are made of atoms connected by chemical bonds.
- The type of bond depends on the difference in electronegativity between two atoms.
Ionic Bonds
- Ionic bonds form when the electronegativity difference is greater than about 2.
- One atom (e.g., chlorine) steals an electron from another atom (e.g., sodium).
- This creates oppositely charged ions (Na⁺ and Cl⁻) that are attracted to each other.
- Ionic bonds involve electrons being taken, not shared.
Covalent Bonds
- Covalent bonds form when the electronegativity difference is less than about 1.7.
- Atoms share electrons instead of transferring them.
- Covalent bonds can be polar or nonpolar, depending on electronegativity difference.
Polar Covalent Bonds
- Polar covalent bonds occur when the electronegativity difference is between 0.5 and 1.7.
- The more electronegative atom pulls the shared electrons closer (e.g., chlorine in H–Cl).
- This creates a partial negative charge (δ–) and a partial positive charge (δ+).
Nonpolar Covalent Bonds
- Nonpolar covalent bonds form when the electronegativity difference is less than 0.5.
- Electrons are shared equally or nearly equally between atoms.
- Atoms in nonpolar covalent bonds do not have partial charges.
Predicting Bond Types
- Nonpolar covalent: electronegativity difference < 0.5, electrons shared evenly.
- Polar covalent: difference between 0.5 and 1.7, electrons shared unevenly.
- Ionic: difference > 2, electrons transferred, ions form.
Key Terms & Definitions
- Chemical Bond — the force holding two atoms together in a molecule.
- Electronegativity — a measure of an atom’s ability to attract shared electrons.
- Ionic Bond — bond where electrons are transferred and ions are formed.
- Covalent Bond — bond where atoms share electrons.
- Polar Covalent Bond — covalent bond with unequal sharing of electrons, causing partial charges.
- Nonpolar Covalent Bond — covalent bond with equal or nearly equal sharing of electrons.
- Ion — a charged particle formed through electron loss or gain.
Action Items / Next Steps
- Practice identifying bond types based on electronegativity differences.
- Review common examples of each bond type.