Which end of a bond attracts electrons more strongly?
You will be able to: Use electronegativity to assign partial charges without confusing them with ion charges.
Which end of a bond attracts electrons more strongly?
Two people can share a blanket unevenly. Similarly, atoms can share electrons unequally: in H–F, electron density is drawn toward F. The analogy is about unequal sharing, not electrons being a solid object.
A useful starting point: Why do salt, water and copper behave differently? →
Words and symbols before equations
- Electronegativity χ
- Relative tendency of a bonded atom to attract shared electrons; dimensionless.
- Partial charge δ
- A fractional imbalance of electron density, not a whole-ion charge.
- Bond dipole
- Separation of positive and negative charge within a bond.
What this picture assumes
Atom A has χ = 2.2. The electron-density marker indicates only the direction of unequal sharing; it is not a calculated charge or electron position.
Read the picture in three steps
- Read the species and labels first. A Lewis line represents two electrons; a spatial stick indicates connectivity. Use the stated quantities and units for numerical comparisons.
- Δχ = 1. Electron density shifts toward B.
- Check what the picture assumes below. Use the Explore task to predict one change before moving a control.
Connect the picture to the chemistry
Compare both atoms on the same electronegativity scale. The more electronegative atom is the δ− end and its partner the δ+ end.
Equal atoms such as those in F₂ share symmetrically, so their bond has no permanent dipole. Increasing the electronegativity difference generally increases unequal sharing for comparable bonds.
Ionic and covalent character form a continuum. A numerical cutoff is a teaching convention, not a universal law. Electronegativity alone does not classify every substance, and a polar bond does not guarantee a polar molecule.
A worked example, step by step
Using χ(H) = 2.2 and χ(F) = 4.0, find the difference and label H–F.
- Define Δχ as the absolute difference on one dimensionless scale.
- Δχ =
- 4.0 − 2.2
- = 1.8.
- F attracts the shared electrons more strongly: Hδ+–Fδ−.
- This indicates a polar bond; it does not mean a free H⁺ and F⁻ pair exists in each HF molecule.
A partial negative charge and an integer ionic charge are different descriptions.
Does a bond between identical atoms have a permanent bond dipole?
Compare with an explanation
No. Both nuclei attract the shared electron density equally by symmetry.
Predict. Change one thing. Explain.
Hold atom A at χ = 2.2. Change χ of atom B through smaller, equal and larger values. Predict where δ− should appear; the displayed imbalance is qualitative.
On narrow screens, swipe or scroll diagrams sideways to read all labels.
Δχ = 1. Electron density shifts toward B.
Atom A has χ = 2.2. The electron-density marker indicates only the direction of unequal sharing; it is not a calculated charge or electron position.
Explain what you noticed: Answer the investigation prompt above. State one observation and explain it using electron accounting, electrostatic interactions or spatial geometry. Identify what the representation cannot tell you.
Apply the idea to a fresh problem Practice →Show what you understand.
Two original questions are a starting check, not proof of mastery. Explain your choice before revealing the answer.
Original written challenge
4 points · self-check · not an official AP questionCompare A–B with χ(A)=2.0, χ(B)=3.0 and C–C with χ(C)=2.5. Compute both differences, label partial charges and state a limit of your conclusion.
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Compare with the answer and four-point rubric
- 1 point: A–B has Δχ = 1.0.
- 1 point: A is δ+ and B is δ−.
- 1 point: C–C has Δχ = 0 and no permanent bond dipole.
- 1 point: Bond polarity alone does not determine a whole molecule’s polarity.
Accept equivalent correct methods and explanations. This is a Refresh Kid teaching rubric, not an official AP scoring guideline.
Retrieve it before you reveal it.
RECALL 1What does δ mean?
A partial charge from unequal electron sharing.
RECALL 2Which atom is δ−?
The more electronegative bonded atom.
RECALL 3Why avoid a universal ionic cutoff?
Bonding lies on a continuum and material properties also matter.
Revisit these tomorrow and a week later. Try a fresh problem and explain why the method applies.
Which end of a bond attracts electrons more strongly?
- Δχ =
- χB − χA
- ; no units.
- The higher-χ atom carries δ− in the bond.
Remember: A partial negative charge and an integer ionic charge are different descriptions.
Conditions: Atom A has χ = 2.2. The electron-density marker indicates only the direction of unequal sharing; it is not a calculated charge or electron position.
Refresh Kid · AP Chemistry Unit 2 · Objectives 2.1.A · Review edition
Framework, scope and review status
Mapped to College Board CED, Topic 2.1, objectives 2.1.A. CED effective Fall 2024, current official file checked September 16, 2026, together with the published clarifications. This is Unit 2: Compound Structure and Properties, Topics 2.1–2.7. The focused lesson breakdown is Refresh Kid’s editorial sequence. Models and original practice are teaching materials, not official AP questions. Numerical potential curves, ion comparisons and orbital-alignment indices state their approximations. Five- and six-domain shapes are included; d-orbital hybridization and molecular-orbital diagrams are not required here. GitHub’s 3D website examples, including the Three.js Mars camera-control example, informed the use of rotatable scenes. Our scientific geometry and viewer code are original; no repository artwork or tutorial code was copied. The self-hosted Three.js library retains its MIT license. Camera rotation does not alter chemistry. See also the official clarifications.
Implementation and automated checks are separate from independent teacher review and observation of students. Both human review stages remain pending. This is a review edition, not a certified or validated assessment.
Optional further resource: College Board’s released questions and scoring guides. Papers can combine units; this link is an archive, not an assignment of every question to this lesson.
Our learn, explore, practice and recall sequence is informed by the IES learning guide. The exact Refresh Kid implementation has not been evaluated for learning effectiveness.
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