---
title: "Bond Polarity — AP Chem Definition & Exam Guide"
description: "Bond polarity is the unequal sharing of electrons in a covalent bond caused by an electronegativity difference. Key for AP Chem Topic 2.7 and molecular polarity."
canonical: "https://fiveable.me/ap-chem/key-terms/bond-polarity"
type: "key-term"
subject: "AP Chemistry"
unit: "Unit 2"
---

# Bond Polarity — AP Chem Definition & Exam Guide

## Definition

Bond polarity is the unequal sharing of electrons in a covalent bond that happens when the two atoms have different electronegativities, leaving the more electronegative atom with a partial negative charge (δ-) and the other atom with a partial positive charge (δ+).

## What It Is

Bond polarity describes what happens when two bonded atoms don't pull on the shared electrons equally. If one atom is more electronegative, the electron [density](/ap-chem/key-terms/density "fv-autolink") shifts toward it. That atom picks up a partial negative charge (written δ-) and the other atom gets a partial positive [charge](/ap-chem/unit-9 "fv-autolink") (δ+). The bigger the electronegativity difference, the more polar the bond. Think of it as a tug-of-war where one atom is stronger, so the rope (the electron pair) sits closer to its side.

In [AP Chem](/ap-chem "fv-autolink"), bond polarity lives in Topic 2.7 alongside Lewis diagrams and VSEPR theory. A polar bond creates a bond dipole, a little arrow of charge separation pointing toward the more electronegative atom. But here's the part the exam loves to test. Polar bonds do NOT automatically make a polar molecule. You have to combine bond polarity with molecular geometry to figure out whether the individual bond dipoles cancel or add up.

## Why It Matters

Bond polarity sits in [Unit 2](/ap-chem/unit-2 "fv-autolink") (Compound Structure and Properties), Topic 2.7, and directly supports learning objective 2.7.A, which asks you to use Lewis diagrams, VSEPR theory, bond orders, and bond polarities together to explain the structural and electron properties of molecules. It's the bridge concept between [electronegativity](/ap-chem/key-terms/electronegativity "fv-autolink") (a periodic trend you learn early in the course) and molecular polarity (which decides intermolecular forces, boiling points, and solubility later in Unit 3). If you can't identify which bonds are polar and which way the electrons lean, you can't predict whether a molecule is polar, and a huge chunk of Units 2 and 3 builds on exactly that skill.

## Connections

### [Molecular polarity (Unit 2)](/ap-chem/key-terms/molecular-polarity)

Bond polarity is the ingredient; [molecular polarity](/ap-chem/key-terms/molecular-polarity "fv-autolink") is the recipe. A molecule is polar only if its bond dipoles don't cancel, which depends on the geometry. CO2 has two polar C=O bonds, but its linear shape makes them cancel, so the molecule is nonpolar.

### [Dipole moment (Unit 2)](/ap-chem/key-terms/dipole-moment)

A [dipole moment](/ap-chem/key-terms/dipole-moment "fv-autolink") is how you measure polarity. Each polar bond contributes a bond dipole, and the vector sum of all of them gives the molecule's net dipole moment. Zero net dipole means a nonpolar molecule, no matter how polar the individual bonds are.

### [Molecular Geometry (Unit 2)](/ap-chem/key-terms/molecular-geometry)

VSEPR geometry decides whether bond dipoles cancel. Symmetric shapes like linear, trigonal planar, and [tetrahedral](/ap-chem/key-terms/tetrahedral "fv-autolink") (with identical outer atoms) cancel their dipoles. Bent and trigonal pyramidal shapes, often caused by lone pairs, don't.

### [Intermolecular forces (Unit 3)](/ap-chem/key-terms/intermolecular-forces)

Bond polarity is the upstream cause of dipole-dipole forces and hydrogen bonding. The polar O-H bond in water is exactly why water hydrogen bonds, which is why it has a weirdly high boiling point. Unit 3 questions about IMFs almost always trace back to bond polarity.

## On the AP Exam

Multiple-choice questions test bond polarity in two main ways. First, ranking questions ask which bond is most polar, and the answer is always the pair with the biggest electronegativity difference. Second, trap questions give you a molecule with polar bonds and ask whether the molecule itself is polar, which forces you to bring in geometry. A classic setup compares CO2 and SO2. Both have polar bonds, but CO2 is linear (dipoles cancel, nonpolar) while SO2 is bent because of a lone pair on sulfur (dipoles don't cancel, polar). On FRQs, bond polarity shows up inside explanations. You might draw a Lewis structure, name the VSEPR geometry, then justify whether the molecule is polar by arguing about whether the bond dipoles cancel. A complete answer names the electronegativity difference, identifies the partial charges, and connects geometry to the net dipole.

## bond polarity vs Molecular polarity

Bond polarity is about one bond; molecular polarity is about the whole molecule. A molecule can be stuffed with polar bonds and still be nonpolar if its geometry makes the bond dipoles cancel. CO2 is the poster child. Its two C=O bonds are polar, but they point in exactly opposite directions in a linear molecule, so the molecule has no net dipole. SO2 has similar polar bonds but a bent shape, so its dipoles add up and the molecule is polar. On the exam, never jump from 'has polar bonds' straight to 'is a polar molecule' without checking geometry.

## Key Takeaways

- Bond polarity comes from a difference in electronegativity between two bonded atoms, and a bigger difference means a more polar bond.
- The more electronegative atom in a polar bond carries a partial negative charge (δ-) and the less electronegative atom carries a partial positive charge (δ+).
- Polar bonds do not guarantee a polar molecule; you have to check the VSEPR geometry to see whether the bond dipoles cancel.
- CO2 is the classic example of a nonpolar molecule with polar bonds, because its linear geometry makes the two C=O dipoles cancel exactly.
- Lone pairs often break the symmetry of a molecule (like the bent shape of SO2 or H2O), which prevents dipoles from canceling and makes the molecule polar.
- Learning objective 2.7.A expects you to combine Lewis diagrams, VSEPR, and bond polarities in one argument, not treat them as separate facts.

## FAQs

### What is bond polarity in AP Chem?

Bond polarity is the unequal sharing of electrons in a covalent bond caused by an electronegativity difference between the two atoms. The more electronegative atom pulls electron density toward itself and gets a partial negative charge, while the other atom becomes partially positive.

### Does having polar bonds mean a molecule is polar?

No, and this is one of the most-tested traps in Unit 2. CO2 has two polar C=O bonds but is nonpolar because its linear geometry makes the bond dipoles cancel. SO2 has similar polar bonds but is polar because its bent shape keeps the dipoles from canceling.

### How is bond polarity different from molecular polarity?

Bond polarity describes one bond, based purely on the electronegativity difference between its two atoms. Molecular polarity describes the whole molecule and depends on both the bond polarities and the geometry, since symmetric shapes can cancel out individual bond dipoles.

### How do you know which bond is more polar?

Compare electronegativity differences. The bond between atoms with the larger electronegativity gap is more polar. For example, H-F is more polar than H-Cl because fluorine is more electronegative than chlorine, so it pulls harder on the shared electrons.

### Is a polar bond the same as an ionic bond?

No. Bonding is a spectrum based on electronegativity difference. A small difference gives a nonpolar covalent bond, a moderate difference gives a polar covalent bond where electrons are shared unequally, and a very large difference (typically metal plus nonmetal) gives an ionic bond where electrons are essentially transferred.

## Related Study Guides

- [2.7 VSEPR and Bond Hybridization](/ap-chem/unit-2/vsepr-bond-hybridization/study-guide/OslsAmh8LcVoqbpnjPAu)

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