Learning objectives
Students should be able to:
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Define first and successive ionisation energies and write the corresponding gaseous equations.
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Explain trends using nuclear charge, distance from the nucleus and electron shielding.
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Explain the effects of subshell energy and electron pairing.
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Interpret successive ionisation energy graphs and relate large jumps to electron configuration.
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Predict and justify differences between selected atoms or ions.
Using the tool
Introduce electron removal
The tool opens with sodium and magnesium set to their first ionisation energies. Animate a removal and identify the starting atom, departing electron and resulting ion. Draw attention to the gaseous state symbols, unchanged nucleus and energy required.
Use Pause, Step or the progress slider to examine the process. The amber electron and highlighted orbital arrow identify the electron being removed.
Investigate periodic trends
Open Periodic trends and select a period or main group. Click graph points to display the corresponding atom and electron configuration, or use Next element to move through the selection.
Start with Period 3 to establish the overall increase, then investigate the decreases from magnesium to aluminium and phosphorus to sulfur. Compare these with the corresponding exceptions in Period 2. Use a group to explore how additional shells and shielding affect first ionisation energy.
Explore successive ionisations
Open Successive, select an element and inspect its graph. Clicking a point shows the exact ionisation process and starting ion.
Ask students to identify how many electrons are removed before a large jump. Sodium, magnesium and aluminium provide useful contrasting examples. Switch between linear and logarithmic scales: the logarithmic scale helps display the wide range of successive energies, but equal vertical intervals represent equal ratios rather than equal differences.
The table provides an alternative way to inspect and select values.
Compare selected atoms and ions
In Compare, choose the element and ionisation number independently for each panel. Useful investigations include:
ComparisonTeaching focusLi IE₁ and Na IE₁Additional shells, distance and shieldingMg IE₁ and Al IE₁Removal from s and p subshellsN IE₁ and O IE₁Repulsion between paired p electronsNa IE₁ and Na IE₂Moving from an outer shell to an inner shellNa IE₂ and Mg IE₂Na⁺ loses a 2p electron; Mg⁺ still has a 3s electronNa IE₂ and Mg IE₃Isoelectronic starting ions with different nuclear charges
Use Predict first before revealing numerical evidence. Students can select which comparison requires more energy, justify their choice and then use Explain to review their reasoning.
Teaching tips and common misconceptions
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IE₂ is one electron removal from a 1+ ion, not the total energy needed to remove two electrons from the neutral atom.
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Ionisation requires energy to overcome attraction between the nucleus and an electron; it is endothermic.
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Nuclear charge remains unchanged during successive ionisation. The electron configuration and electron–electron interactions change.
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Avoid accepting “a full shell is stable” as a complete explanation. Require students to identify the shell or subshell involved and explain the relevant attraction, shielding or repulsion.
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For isoelectronic species, compare proton numbers: the species with greater nuclear charge generally holds the same electron arrangement more strongly.
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The shell diagrams are schematic, not measured atomic radii or literal electron paths. Orbital boxes represent occupancy and pairing, not orbital shape.
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Animation speed does not indicate ionisation energy. Use the numerical values and graphs for energy comparisons.
Display and independent use
Use Focus to enlarge the workspace by hiding the explanation strip and footer, and full screen where supported. Display offers three colour schemes and switches for configurations, orbital boxes and particle counts.
For independent work, ask students to record a prediction, supporting configuration and explanation before revealing the evidence. The same controls support teacher-led discussion and student-paced exploration. The HTML works offline; the embedded guide and Data & model panel explain the controls, data and model limitations.