The Periodic Table: chemical periodicity — AS & A Level Chemistry (9701) questions by topic
Period 3 trends and structure-property links define this topic: identifying elements from ionisation-energy and conductivity clues, deducing the acid-base nature and structure of oxides such as SO2, and explaining melting-point differences between giant covalent and simple molecular substances.
Identify, deduce, state, express and explain are the top command words across 59 questions from 2023 to 2025 papers, worth from 1 to 20 marks, the widest mark spread in this syllabus set, so short recall items sit alongside extended explanations in the same topic. Submitting structural and bonding explanations for instant marking exposes exactly which state symbol or shielding argument was missing before it recurs across a full periodicity essay.
What examiners look for
- Examiners repeatedly note that state symbols, essential in ionisation-energy equations, were included less often than expected.
- A common misconception placed intermolecular forces in silicon, or omitted them from sulfur, when explaining melting-point differences.
- Reports flag weaker answers that identified a general periodic trend without also explaining sulfur's lower first ionisation energy relative to phosphorus.
- Strong scripts correctly identified phosphorus's ionisation energy of 1060 kJ mol-1 and explained both the general trend and the effect of spin-pair repulsion on sulfur's paired p electrons.
- Candidates who described an SCl2 molecule's shape as bent or V-shaped, rather than linear, were rewarded.
May–June 2025, Paper 11
The table shows some data for the elements in Period 3 of the Periodic Table. element melting point/K electrical conductivity sodium 371 good magnesium 922 good aluminium 933 good…
Answer this question and get it marked →Compound X contains two Period 3 elements, Y and Z. Compound X reacts with water to form only two products: a slightly soluble hydroxide and compound Q. Q is a compound of element…
Answer this question and get it marked →May–June 2025, Paper 12
The oxide and chloride of an element X are separately mixed with water. The two resulting solutions have the same effect on litmus. What could element X be? A Al B Ca C Na D P
Answer this question and get it marked →Compound M is a white solid. It is the chloride of a Period 3 element. reaction observation compound M + non-polar solvent colourless solution compound M added a little at a time…
Answer this question and get it marked →Elements Y and Z are both in Period 3. Element Y has the smallest atomic radius in Period 3. There are only two elements in Period 3 that have a lower melting point than element…
Answer this question and get it marked →May–June 2025, Paper 13
Three statements about the chemical periodicity of Period 3 oxides are listed. 1 The maximum oxidation state of the Period 3 elements in their oxides increases from sodium to…
Answer this question and get it marked →Which set of three elements contains a single element that has both the highest melting point and the lowest electrical conductivity of the three elements in the set? A magnesium,…
Answer this question and get it marked →May–June 2025, Paper 14
X, Y and Z are elements in Period 3 of the Periodic Table. The results of some experiments carried out with compounds of these elements are shown. Element X: oxide + H2O → no…
Answer this question and get it marked →What increases for each successive element in Period 3 from sodium to sulfur? A the highest oxidation number of the element seen in an oxide B the melting point of the elements C…
Answer this question and get it marked →May–June 2025, Paper 23
A Period 3 oxide produces a solution with a pH greater than 10 when it is added to water. State the formula of the oxide.
Answer this question and get it marked →May–June 2024, Paper 11
Elements Y and Z are both in Period 3 of the Periodic Table. When the chloride of element Y is added to water, it reacts and a solution of pH 2 is produced. When the chloride of…
Answer this question and get it marked →Aluminium, silicon and phosphorus are elements in Period 3 of the Periodic Table. Each element forms an oxide. Which row is correct? Al2O3 SiO2 P4O10 --- --- --- --- A basic…
Answer this question and get it marked →Which statement is correct? A The atomic radius of silicon is larger than that of aluminium. B The boiling point of chlorine is higher than that of silicon. C The first ionisation…
Answer this question and get it marked →May–June 2024, Paper 12
Which statement is correct? A Aluminium chloride has a giant ionic lattice of Al^3+ and Cl^- ions. B Sodium chloride dissolves in water, forming hydrogen chloride and sodium…
Answer this question and get it marked →Sodium is added to water to form solution Y. The pH of solution Y is measured. When powdered substance X is added to solution Y, the pH falls. Which two compounds could each be…
Answer this question and get it marked →Which statement is correct? A Adding sodium oxide to water gives a lower pH solution than adding silicon oxide to water. B The oxidation state of sodium in its chloride is higher…
Answer this question and get it marked →May–June 2024, Paper 13
Magnesium, aluminium and silicon are elements in the Periodic Table. Each element forms an oxide. Which row is correct? MgO Al2O3 SiO2 --- --- --- --- A basic amphoteric…
Answer this question and get it marked →Which statement correctly describes what happens when silicon tetrachloride is added to water? A The SiCl4 dissolves to give a neutral solution only. B The SiCl4 reacts to give an…
Answer this question and get it marked →X and Y are two elements from Period 3 of the Periodic Table. Element X has a higher electrical conductivity than element Y. Element Y has a higher melting point than element X.…
Answer this question and get it marked →May–June 2024, Paper 21
Sulfur chloride, SCl2, is a liquid at room temperature. When SCl2 is added to water, misty fumes are seen and a solution is made that turns universal indicator red. Identify the…
Answer this question and get it marked →October–November 2024, Paper 11
In this question Q is used to represent a halogen atom. Magnesium and calcium each form a compound with chlorine and a compound with bromine. One of these compounds contains: -…
Answer this question and get it marked →The graphs show trends in four physical properties of elements in Period 3, excluding argon. Which graph has electronegativity on the y-axis? Four graphs A, B, C and D plot a…
Answer this question and get it marked →What are the acid–base nature and structure of SO₂? acid–base nature structure --- --- --- A acidic giant covalent lattice B acidic simple molecular C basic giant covalent lattice…
Answer this question and get it marked →Elements X and Y are in Period 3 of the Periodic Table. Element X is either phosphorus or sulfur. Element Y is either sodium or magnesium. Element X forms an oxide that reacts…
Answer this question and get it marked →Q is a semi-conductor. The chloride of Q reacts with water to form white fumes and an acidic solution. Which Period 3 element is Q? A magnesium B aluminium C silicon D phosphorus
Answer this question and get it marked →October–November 2024, Paper 12
Which oxide is insoluble in aqueous sodium hydroxide? A MgO B Al₂O₃ C P₄O₁₀ D SO₂
Answer this question and get it marked →Sodium and sulfur are burned separately in oxygen. Each reaction has a distinctive coloured flame. Which row is correct? Na + O₂ S + O₂ --- --- --- A white flame blue flame B…
Answer this question and get it marked →X and Y are elements in Period 3 of the Periodic Table. Y has a greater atomic number than X. The stable ion formed by Y has a greater radius than the stable ion formed by X. The…
Answer this question and get it marked →October–November 2024, Paper 13
In this question Q is used to represent a halogen atom. Magnesium and calcium each form a compound with chlorine and a compound with bromine. One of these compounds contains: -…
Answer this question and get it marked →The graphs show trends in four physical properties of elements in Period 3, excluding argon. Which graph has electronegativity on the y-axis? Four graphs A, B, C and D plot a…
Answer this question and get it marked →What are the acid–base nature and structure of SO₂? acid–base nature structure --- --- --- A acidic giant covalent lattice B acidic simple molecular C basic giant covalent lattice…
Answer this question and get it marked →Elements X and Y are in Period 3 of the Periodic Table. Element X is either phosphorus or sulfur. Element Y is either sodium or magnesium. Element X forms an oxide that reacts…
Answer this question and get it marked →Q is a semi-conductor. The chloride of Q reacts with water to form white fumes and an acidic solution. Which Period 3 element is Q? A magnesium B aluminium C silicon D phosphorus
Answer this question and get it marked →October–November 2024, Paper 23
The Group 14 elements show a change from non-metallic to metallic character down the group. Table 3.1 shows some properties of two Group 14 elements, C and Sn, in their standard…
Answer this question and get it marked →February–March 2023, Paper 12
Two Period 3 elements, X and Y, burn separately in oxygen to form solid oxides. The oxide of X is insoluble in water. The oxide of Y dissolves in water to form a solution which…
Answer this question and get it marked →Which row describes the structure and bonding of SiO2 and SiCl4? SiO2 structure SiO2 bonding SiCl4 structure SiCl4 bonding --- --- --- --- --- A giant covalent giant covalent B…
Answer this question and get it marked →V and Z are both elements in Period 3 of the Periodic Table. Each element forms one stable ion that does not contain another element. The atomic radius of each element and the…
Answer this question and get it marked →May–June 2023, Paper 11
Three statements about potassium and chlorine and their ions are listed. 1 The atomic radius of a potassium atom is greater than the atomic radius of a chlorine atom. 2 The first…
Answer this question and get it marked →SiO2 has a melting point of 1713 °C. It reacts with hot NaOH(aq) to form sodium silicate, Na2SiO3, and water. No reaction occurs when SiO2 is added to hot H2SO4(aq). What can be…
Answer this question and get it marked →Element X has the second largest atomic radius in its period. An atom of X has three occupied electron shells only. The oxide of X is shaken with water. What could be the pH of…
Answer this question and get it marked →The diagram shows the melting points of eight elements with consecutive atomic numbers. The graph plots melting point / K against atomic number, with eight points labelled; A and…
Answer this question and get it marked →May–June 2023, Paper 12
L, M and N are three different elements from Period 3 of the Periodic Table. L is the element whose atoms have three unpaired electrons in its 3p sub-shell. M is the element with…
Answer this question and get it marked →In reactions 1 and 2, X represents an element in Period 3. In each reaction, X is forming a chloride or oxide in which X is in its highest oxidation state. reaction 1: chlorine +…
Answer this question and get it marked →Sodium, magnesium, aluminium, silicon and phosphorus are all elements in Period 3 of the Periodic Table. Three statements about the oxides and chlorides of these elements are…
Answer this question and get it marked →May–June 2023, Paper 13
L and M are elements in Period 3 of the Periodic Table. Neither element is argon. Information about the Pauling electronegativity values of L and M is given. element Pauling…
Answer this question and get it marked →The elements magnesium and phosphorus are reacted separately with an excess of oxygen to form their oxides. Each oxide is then added separately to water and the pH values of the…
Answer this question and get it marked →May–June 2023, Paper 21
Chlorine is a very reactive element. Chlorine reacts with silicon to form silicon(IV) chloride. Describe the appearance of silicon(IV) chloride at room temperature and pressure.…
Answer this question and get it marked →May–June 2023, Paper 22
Chlorine is a reactive element. It forms many compounds. Complete Table 2.1 to show the maximum oxidation number of the elements Na, Mg, Al, Si and P in their chlorides.
Answer this question and get it marked →May–June 2023, Paper 23
The reaction of pure aluminium with water is only observed if the aluminium oxide layer is removed first. When pure aluminium is added to cold water, bubbles of gas are seen.…
Answer this question and get it marked →October–November 2023, Paper 11
X, Y and Z are elements all found within Groups 13, 14 and 15 of the Periodic Table. X is in the same group as Y. Y and Z are in Period 3. The first ionisation energy of X is…
Answer this question and get it marked →Which row about silicon, Si, and magnesium, Mg, and their ions is correct? A: Si has a greater atomic radius than Mg, because Si has electrons in 3p orbitals and Mg has electrons…
Answer this question and get it marked →Bromocresol green is an acid-base indicator; below pH 3.8 it is yellow, above pH 5.4 it is blue, and between these values it is green. Bromocresol green is added to the aqueous…
Answer this question and get it marked →October–November 2023, Paper 12
Which row gives the best description of the variations in the melting points and the first ionisation energies of the elements in Period 3 from sodium to argon? A: melting points…
Answer this question and get it marked →X and Y are atoms of different elements in Period 3 of the Periodic Table; neither X nor Y is argon. X is a non-metal. X has a greater atomic radius than Y. Which statement is…
Answer this question and get it marked →Four mixtures are added to four separate 50 cm3 samples of water and stirred. Which mixture results in a solution with the highest pH? A: 1.0 g of aluminium oxide and 1.0 g of…
Answer this question and get it marked →October–November 2023, Paper 13
X, Y and Z are elements all found within Groups 13, 14 and 15 of the Periodic Table. X is in the same group in the Periodic Table as Y. Y and Z are in Period 3. The first…
Answer this question and get it marked →Which row about silicon, Si, and magnesium, Mg, and their ions is correct? comparison of silicon and magnesium explanation --- --- --- A Si has a greater atomic radius than Mg. Si…
Answer this question and get it marked →Bromocresol green is an acid-base indicator. Below a pH of 3.8 it is yellow. Above a pH of 5.4 it is blue. Between these values it is green. Bromocresol green is added to the…
Answer this question and get it marked →October–November 2023, Paper 22
The elements silicon, phosphorus and sulfur are in Period 3 of the Periodic Table. Describe the variation in atomic radius from silicon to sulfur.
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