Is the advanced mode required by AQA or OCR A?

The core first-ionisation-energy and successive-ionisation reasoning is standard A-level chemistry. Advanced mode deliberately goes further, for example by comparing second and third ionisation energies across a period, as stretch and synoptic practice.

Why do the first ionisation energies dip at aluminium and sulfur?

Aluminium loses a higher-energy 3p electron rather than a 3s electron. In sulfur, one 3p orbital contains a paired set of electrons, and repulsion within that orbital makes one electron easier to remove.

How do successive ionisation energies show the number of outer electrons?

A very large increase appears when ionisation starts removing an electron from the next principal shell. The number of electrons removed before that jump gives the number in the outer shell.

AQA · OCR A · A-level Chemistry

Ionisation energy questions and graph practice

If you can spot the pattern and your explanation still feels vague, start here. Practise first-ionisation trends, missing graph points, successive-ionisation jumps and nth-ionisation equations; advanced mode adds second and third ionisation energies across a period.

Start with graph questions Advanced challenge

Choose the thing that is costing marks

The tools use one data set and separate the different reasoning jobs. Mixed practice brings them together later.

Data plotterChoose a period, group or element and plot 1st, 2nd, 3rd and higher ionisation energies instantly. teacher displayperiod / groupsuccessive IE Explore First IE trendsPredict and explain first-ionisation-energy trends across periods and down groups, including the familiar s→p and paired-p anomalies. period trendsgroup trendsAl / S anomalies Practise Graph questionsPlot missing first-ionisation-energy points, interpret discontinuities and use graphs as evidence for electron structure. plot missing pointsread anomaliesevidence from graphs Practise Successive IEFind large jumps, infer outer electrons, identify an element and connect the pattern to ions and compound formulae. large jumpsouter electronsidentify element Practise IE equationsBuild first, second, third and higher ionisation equations with the correct starting charge, product charge and gaseous state symbols. nth IE equationionic chargestate symbols Practise Advanced challengeStretch questions on second and third ionisation energies across a period, isoelectronic species, nested shell jumps and synoptic electronic-structure reasoning. 2nd and 3rd IE trendsisoelectronic speciessynoptic reasoning Practise Mixed practiceA changing mixture of graphs, equations, trends, anomalies and successive-ionisation-energy deductions. mixed retrievalexam reasoningelectronic structure Practise

What a good explanation actually needs

Across a period, I’d keep the explanation as a chain: nuclear charge increases, shielding stays similar because the outer electron remains in the same principal shell, attraction to the nucleus strengthens, and more energy is needed to remove the electron.

For a dip, name the specific electronic change. The first p electron is higher in energy than the preceding s electron; a paired p electron experiences repulsion from the other electron in the same orbital.

Successive IE7381451773310543A large jump after the second electron is the clue: two outer-shell electrons.

Advanced mode adds second- and third-ionisation patterns

Compare second and third ionisation energies across a period, decide which electron is being removed from each ion, and explain the sharp discontinuities when the next electron comes from an inner shell. Use these as stretch practice once first-ionisation reasoning is secure.

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