A chemical bond is the attractive force that holds two atoms or ions together as a unit, formed when atoms share valence electrons (covalent) or transfer them (ionic). In AP Chem, the electronegativity difference between the bonded atoms tells you which type of bond you have.
A chemical bond is the force of attraction that locks two atoms or ions together. It happens because valence electrons get shared between atoms or transferred from one atom to another, and the resulting attraction between positive nuclei and negative electrons lowers the system's energy. That energy part matters. Atoms bond because the bonded arrangement is more stable (lower potential energy) than the separated atoms. On a potential energy diagram, the bond length is the internuclear distance at the bottom of the energy well, and the bond energy is how deep that well is.
The AP exam cares less about memorizing bond types and more about predicting them. The tool for that is electronegativity, which increases left to right across a period and decreases down a group (you can explain why using Coulomb's law and the shell model). When two atoms have similar electronegativities, they share electrons fairly evenly and form a nonpolar covalent bond (C-H bonds count as effectively nonpolar). A bigger electronegativity gap means unequal sharing, so you get a polar covalent bond. A metal paired with a nonmetal usually means full electron transfer, which gives an ionic bond. Think of it as a spectrum of electron tug-of-war, from a fair share to a complete steal.
Chemical bonds anchor Topic 2.1 (Types of Chemical Bonds) in Unit 2: Compound Structure and Properties, supporting learning objective 2.1.A, which asks you to explain how the type of bonding relates to the properties of the elements involved. This is one of the most load-bearing ideas in the whole course. Once you can classify a bond as nonpolar covalent, polar covalent, or ionic using electronegativity trends (2.1.A.1 through 2.1.A.3), you unlock everything downstream: Lewis structures, molecular geometry, polarity, and eventually why substances have the melting points, solubilities, and conductivities they do. If you can't classify the bond, the rest of Unit 2 and Unit 3 doesn't make sense.
Keep studying AP Chemistry Unit 2
Coulomb's Law (Unit 1 & Unit 2)
Coulomb's law is the physics underneath every bond. The attraction between nuclei and electrons depends on charge and distance, which is exactly why electronegativity increases across a period (more protons, same shell) and why smaller, more highly charged ions form stronger ionic bonds.
Covalent Bond and Ionic Bond (Unit 2)
These are the two main flavors of chemical bond, and the dividing line is electronegativity difference. Similar electronegativities mean sharing (covalent); a metal handing electrons to a nonmetal means transfer (ionic). The exam loves asking you to justify the classification, not just name it.
Molecular Geometry and Polarity (Unit 2)
Individual bond polarity is only half the story. Whether a whole molecule is polar depends on how those bond dipoles are arranged in 3D space, so a molecule like CO₂ can have polar bonds but be nonpolar overall because the dipoles cancel.
Intermolecular Forces (Unit 3)
Bonds hold atoms together within a molecule; IMFs attract separate molecules to each other. The bond polarity you figure out in Unit 2 determines which IMFs show up in Unit 3, which then controls boiling points, vapor pressure, and solubility.
Multiple-choice questions usually test this term through prediction and justification. You'll see stems asking why fluorine attracts shared electrons more strongly than chlorine (answer with Coulomb's law: fluorine's valence electrons are in a shell closer to the nucleus), what valence electrons do (they're the electrons involved in bonding), or how to read a potential energy diagram for a molecule like H₂, where the minimum at 74 pm and -436 kJ/mol gives you the bond length and bond energy. No released FRQ asks you to define "chemical bond" outright, but bond-type reasoning is everywhere in FRQs. You're expected to classify a bond from electronegativity values, connect bond type to physical properties like melting point or conductivity, and explain trends in bond strength using charge and distance. The move that earns points is the explanation, not the label.
Chemical bonds are intramolecular. They hold atoms together inside a molecule or formula unit. IMFs are the much weaker attractions between separate molecules. This distinction decides points on the exam. When water boils, you break hydrogen bonds (an IMF) between water molecules, not the O-H covalent bonds inside them. Saying a phase change breaks chemical bonds is one of the most common ways to lose FRQ credit in Unit 3.
A chemical bond is the attractive force between atoms or ions created by sharing or transferring valence electrons, and bonded atoms are lower in energy than separated atoms.
Electronegativity difference predicts bond type: similar values give a nonpolar covalent bond, a moderate gap gives a polar covalent bond, and a metal-nonmetal pairing typically gives an ionic bond.
Electronegativity increases left to right across a period and decreases down a group, and you can explain both trends with Coulomb's law and the shell model.
C-H bonds count as effectively nonpolar on the AP exam even though carbon is slightly more electronegative than hydrogen.
On a potential energy diagram, the minimum of the curve gives the bond length (x-axis) and the bond energy (depth of the well on the y-axis).
Melting or boiling a molecular substance breaks intermolecular forces, not the chemical bonds inside the molecules.
It's the attractive force holding two atoms or ions together, formed by sharing valence electrons (covalent) or transferring them (ionic). It's the foundation of Topic 2.1 and learning objective 2.1.A.
No. Boiling breaks the hydrogen bonds (intermolecular forces) between water molecules, while the covalent O-H bonds inside each molecule stay intact. Mixing these up is a classic way to lose FRQ points.
Compare electronegativities. Atoms with nearly equal values share electrons evenly (nonpolar covalent), a noticeable gap means unequal sharing (polar covalent), and a metal bonded to a nonmetal usually means full electron transfer (ionic). The AP exam expects the reasoning, not a memorized cutoff number.
A chemical bond holds atoms together within a molecule; an intermolecular force is a weaker attraction between separate molecules. Bonds are broken in chemical reactions, while IMFs are overcome in physical changes like melting and boiling.
Fluorine's valence shell sits closer to its nucleus, so by Coulomb's law the attraction between its nucleus and shared electrons is stronger. That's why electronegativity decreases down a group, and it's a frequent MCQ setup.
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