Learning objectives
Students should be able to:
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Define electronegativity as an atom’s ability to attract bonding electrons in a covalent bond.
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Interpret Pauling values and explain general periodic trends.
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Identify partial charges and the direction of a bond dipole.
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Use molecular shape and bond polarity to explain whether a molecule has an overall dipole.
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Distinguish between local polar bonds and the overall polarity of a molecule.
Using the interactive tool
1. Bond polarity
Begin with H–H to establish equal sharing, then compare H–Cl and H–F. Ask students to predict which atom attracts the bonding electrons more strongly before selecting Reveal polarity.
Switch between Dot & cross and Electron cloud. Use Play, Pause, Step and the slider to examine the distribution gradually. Emphasise that the bond view isolates one shared pair; it is not a complete electron diagram.
2. Periodic trends
Ask students to predict the trends before revealing the values and colours. Select elements across a period or down a group and explain the patterns using nuclear charge, shielding and distance from the nucleus.
The table contains selected main-group elements and uses group numbers 1–18. Pauling values have no units; examination data may use different rounding.
3. Molecular dipoles
Work through Shape → Regions → Overall, asking students to predict each stage.
Use Structure to inspect the molecular geometry, then Charge map to reveal the distribution:
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Purple: electron-rich, partially negative regions.
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Coral: electron-poor, partially positive regions.
Rotate the models to reinforce that polarity depends on the three-dimensional arrangement. Bond arrows can be added to connect the colour distribution with conventional dipole notation.
4. Compare two molecules
Use the independent left and right selectors to investigate useful contrasts:
ComparisonTeaching focusCO₂ and H₂OPolar bonds can cancel in a linear arrangement but not in a bent arrangement.BF₃ and NH₃Trigonal planar and pyramidal arrangements produce different overall outcomes.CCl₄ and CH₃ClA tetrahedral shape alone does not determine polarity; the surrounding atoms matter.CCl₄ and CH₂Cl₂Two C–Cl bonds are not opposite in a tetrahedral molecule.
5. Build the charge centres
At the Overall stage, use Build centres, Pause, Replay, Reset or the slider. The markers combine to show the average positions of positive and negative partial charge.
Coincident centres indicate no overall dipole; separated centres indicate an overall dipole. Draw attention to the coloured regions remaining visible: cancellation does not remove the polar bonds.
The moving markers are a mathematical construction, not electrons moving through the molecule.
6. Investigate bond angle
Select the AB₂ lab and vary the angle while keeping the two bond polarities equal. At 180°, the dipoles cancel; bending the arrangement produces an overall dipole.
Two AB₂ models can be compared with independent angle sliders. This is a hypothetical geometry investigation, not a real molecule changing into another substance.
7. Polarity detective
Use the eight prediction questions for discussion, independent practice or a final check. Ask students to justify their choices before checking, then use the explanatory feedback to correct their reasoning.
Teaching tips and common misconceptions
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A polar molecule remains electrically neutral overall.
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Partial charges, δ+ and δ−, are not full ionic charges.
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Dots and crosses identify electron origins, not different types of electron.
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Polar bonds do not automatically produce a polar molecule.
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“Symmetrical” requires consideration of both molecular shape and the identities of the surrounding atoms.
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Rotating a model changes the view, not its polarity.
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C–H bonds have a small electronegativity difference and are often treated as effectively non-polar at this level.
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Avoid treating a single electronegativity-difference threshold as a universal boundary between ionic and covalent bonding.
Model limitations
The clouds and charge maps are qualitative teaching models, not calculated orbitals or electrostatic-potential surfaces. Colours, partial-charge markers and arrow lengths should not be used to calculate or compare measured dipole moments. Molecular geometries and lone-pair representations are simplified.
Display and independent learning
Use Focus view or Full screen for projection. Drag the models or use the arrow keys to rotate them; Reset view restores a clear starting angle.
For independent work, ask students to record a prediction, inspect the model, reveal the explanation and revise their answer. All teaching features work offline; only the external reference links require internet access.