A-Level Chemistry: Periodicity, Group 2 and Group 7

Inorganic trend questions are the most pattern-rich territory in A-Level Chemistry: the marks go to those who can both state the trend and explain the structure behind it. This quiz covers Period 3, Group 2 and Group 7 — the three trend systems every specification examines.

The Period 3 questions target the explanations rather than the bare facts: why silicon's melting point towers over phosphorus's (giant covalent lattice against simple P₄ molecules), and both canonical ionisation-energy dips — magnesium to aluminium (the 3p electron above 3s) and phosphorus to sulfur (paired-electron repulsion) — each tested through its reason, with the electron configurations given in the question so the reasoning is the skill.

The Group 2 questions cover the down-group trends that must be kept straight in pairs: hydroxide solubility rising while sulfate solubility falls, and the practical chemistry hanging off them, with magnesium hydroxide's antacid role as the applied example.

Group 7 gets the fullest treatment: boiling points rising with van der Waals strength, electronegativity falling with radius, oxidising power demonstrated through displacement (chlorine turning potassium bromide solution orange), the silver nitrate/ammonia halide identification scheme, and both chlorine disproportionations — in water to HCl and HClO, and in cold dilute sodium hydroxide to chloride and chlorate(I), with the oxidation-state bookkeeping (0 to −1 and +1 simultaneously) made explicit.

The blind-solver verification pass returned complete agreement across all ten questions. Explanations consistently follow the state-the-trend, name-the-cause structure that inorganic mark schemes reward.

• Explain Period 3 melting point and ionisation energy patterns structurally
• Keep Group 2 hydroxide and sulfate solubility trends straight
• Rank halogen oxidising power and predict displacement outcomes
• Apply the silver nitrate and ammonia halide identification scheme
• Track oxidation states through chlorine's disproportionation reactions

Aligned to the inorganic core of the DfE A level science subject content: periodicity across Period 3, Group 2 trends and uses, and Group 7 oxidising ability, tests and disproportionation.