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CAIE A Level Chemistry 9701

The Periodic Table: chemical periodicity questions

Exam-style questions on The Periodic Table: chemical periodicity, ordered from foundation to challenge. Pick one, write your answer the way you would in the exam, and it comes back marked against the mark scheme, point by point.

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Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.

  1. Compare5 marksStandardCompare the physical properties of sodium and chlorine, two elements in Period 3. In your answer, refer to: atomic radii the ionic radii of their common ions, Na⁺ and Cl⁻ melting points electrical conductivities…
  2. Explain4 marksStandardConsider the oxides of the elements sodium to sulfur in Period 3: Na2O, MgO, Al2O3, P4O10, SO2 and SO3, and the chlorides NaCl, MgCl2, AlCl3, SiCl4 and PCl5. Explain why the oxidation number of the element in the oxide…
  3. Explain4 marksStandardAn unknown element X is in Period 3 of the Periodic Table. It is a grey solid with a metallic lustre. It reacts with oxygen to form an oxide, XO2, which is a hard solid with a very high melting point. The oxide does…
  4. Compare5 marksStandardPhosphorus(V) chloride, PCl5, reacts vigorously with water to form two acids. Compare the reaction of PCl5 with water with the reactions of NaCl and MgCl2 with water. In your answer include: the equation for the…
  5. Explain4 marksStandardAn unknown element X is in Period 3 of the Periodic Table. Its oxide, XO2, is a solid at room temperature and dissolves in water to form a solution of pH 4. X reacts with chlorine to form a chloride with the formula…
  6. Suggest4 marksStandardAluminium hydroxide, Al(OH)3, is insoluble in water. When dilute hydrochloric acid is added to a suspension of aluminium hydroxide, the solid dissolves. When aqueous sodium hydroxide is added to a separate suspension…
  7. Describe5 marksStandardDescribe the reaction of magnesium with steam. Include observations, an equation, and the pH of the resulting solution.
  8. Compare5 marksStandardAluminium oxide is an amphoteric oxide. Compare its acid-base behaviour with that of sodium oxide, and explain the difference in terms of the bonding and electronegativity of the two elements.
  9. Suggest4 marksStandardTwo elements, X and Y, are each added separately to cold water. X reacts rapidly with cold water, producing a colourless gas that burns with a squeaky pop. The resulting solution turns universal indicator purple. Y…
  10. Describe5 marksStandardDescribe the trend in atomic radius of the elements across Period 3 (sodium to argon) and explain this trend in terms of the structure and bonding of the atoms.
  11. Compare5 marksStandardSodium, magnesium, aluminium and sulfur are elements in Period 3. Compare the melting points of these four elements, and explain the differences in terms of their structure and bonding.
  12. Explain4 marksStandardThe table below shows the approximate pH values of the solutions formed when the oxides of the Period 3 elements (from Na to S) are added separately to water. Oxide pH of solution Na2O 13 MgO 10 Al2O3 7 SiO2 7 P4O10 2…
  13. Explain4 marksStandardThe electrical conductivities of the elements of Period 3 are not the same. Explain, in terms of structure and bonding, why the electrical conductivity of sodium is much greater than that of sulfur, and why the…
  14. Describe5 marksStandardSodium oxide, Na2O, and sulfur dioxide, SO2, are both oxides of elements in Period 3. Describe what happens when each oxide is added to water, and explain why the pH of the resulting solution differs. Write equations…
  15. Explain4 marksStandardThe electrical conductivity of the elements across Period 3 (sodium to argon) changes in a regular way. Explain this variation in terms of the structure and bonding of the elements.
  16. Suggest4 marksStandardThe table shows the ionic radii of some Period 3 ions. Ion Ionic radius / nm Na+ 0.102 ceMg^2+ 0.072 ceAl^3+ 0.054 ceSi^4+ 0.041 ceP^3- 0.212 ceS^2- 0.184 Cl- 0.181 Suggest reasons for the decrease in ionic radius from…
  17. Explain4 marksStandardOxides of the elements sodium to sulfur in Period 3 include Na2O, MgO, Al2O3, P4O10 and SO2. Explain the trend in the oxidation number of the element combined with oxygen in these oxides, in terms of the electron…
  18. Explain4 marksStandardThe oxides of the period 3 elements sodium, magnesium, aluminium, phosphorus and sulfur show a range of oxidation numbers. Explain how the oxidation number of the element in each oxide is related to the number of outer…
  19. Suggest4 marksStandardSodium and magnesium are both metals in Period 3. The melting point of sodium is 98 °C and that of magnesium is 649 °C. Suggest, in terms of structure and bonding, why the melting point of magnesium is much higher than…
  20. Compare5 marksStandardThe oxides of the elements in Period 3 (Na2O, MgO, Al2O3, P4O10, SO2, SO3) show a trend in their reactions with water and their acid-base behaviour. Compare the behaviour of these oxides when added to water. Include…
  21. Suggest4 marksStandardAn unknown element X forms an oxide that dissolves in both dilute hydrochloric acid and dilute sodium hydroxide. The chloride of X is a solid with a high melting point. Suggest what this information indicates about the…
  22. Suggest4 marksStandardExplain, in terms of bonding and electronegativity, why SiCl4 reacts with water but CCl4 does not.
  23. Describe5 marksStandardSilicon has a melting point of 1414 °C. Describe how the melting point and electrical conductivity of the period 3 elements vary from sodium to argon, and explain silicon's high melting point in terms of its structure…
  24. Compare5 marksStandardSulfur exists as S8 molecules and argon exists as separate atoms. Compare the melting points and electrical conductivities of sulfur and argon, and explain your answers in terms of the structure and bonding of the two…
  25. Compare5 marksStandardThe table below shows some properties of two unknown elements, X and Y. Property X Y Melting point / °C 97.8 –101.5 Electrical conductivity of solid good poor Reaction with water vigorous reaction producing a gas that…
  26. Explain4 marksStandardThe table shows the melting points of the elements sodium to argon in Period 3. Element Na Mg Al Si P S Cl Ar Melting point / K 371 922 933 1687 317 388 172 84 Explain the trend in melting point from sodium to argon.
  27. Describe5 marksStandardAn unknown element X is a solid at room temperature. A sample of X conducts electricity when solid, but when X is melted, the liquid also conducts electricity. X does not react with water. Describe what these…
  28. Explain4 marksStandardSilicon and sulfur are elements in Period 3. Their melting points and electrical conductivities are very different. Explain the differences in melting point and electrical conductivity between silicon and sulfur in…
  29. Compare5 marksStandardThe melting points of the elements in Group 14 are given below. Element Melting point / °C C (diamond) 3550 Si 1410 Ge 937 Sn 232 Pb 327 Compare the melting points of these elements and explain the trend.
  30. Explain7 marksChallengeThe melting points of the elements sodium to argon in Period 3 are shown. Element Na Mg Al Si P S Cl Ar Melting point / K 371 922 933 1687 317 388 172 84 Explain the variation in melting point across these elements…
  31. Suggest5 marksChallengeSodium and magnesium are both metallic elements in Period 3. The melting point of sodium is 98 °C, while that of magnesium is 650 °C. At room temperature, both conduct electricity, but magnesium is the better…
  32. Describe5 marksChallengeSodium oxide, Na2O, reacts with water to form a solution. Sulfur dioxide, SO2, also reacts with water. Describe the reactions of these two oxides with water, including the equations, and compare the pH of the two…
  33. Describe7 marksChallengeA student reacts the period 3 elements magnesium and silicon separately with steam, and separately with chlorine gas. (a) Write the equation for the reaction of magnesium with steam, and state two observations that…
  34. Describe7 marksChallengeWith reference to the elements in Period 3, describe the periodicity in atomic radius, ionic radius, melting point and electrical conductivity. Explain the variations in melting point and electrical conductivity in…
  35. Suggest6 marksChallengeThe table shows the ionic radii of some Period 3 ions. Ion Ionic radius / nm Na⁺ 0.095 Mg²⁺ 0.065 Al³⁺ 0.050 Si⁴⁺ 0.041 P³⁻ 0.212 S²⁻ 0.184 Cl⁻ 0.181 Suggest why the ionic radius of the positive ions decreases from Na⁺…
  36. Describe7 marksChallengeDescribe the reactions of the chlorides NaCl, MgCl2, AlCl3, SiCl4 and PCl5 with water. For each chloride, write an equation for any reaction that takes place and state the approximate pH of the resulting solution…
  37. Compare7 marksChallengeThe melting points of the elements sodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine and argon vary across Period 3. Compare the melting points of these elements, and explain the variation in terms of…
  38. Compare6 marksChallengeAluminium oxide, Al2O3, reacts with both dilute hydrochloric acid and aqueous sodium hydroxide. Compare these two reactions. In your answer, include the equations for both reactions and state the type of behaviour that…
  39. Explain7 marksChallengeA student reacts samples of the Period 3 elements sodium, magnesium, aluminium, silicon, phosphorus and sulfur with oxygen. In separate experiments, the student also reacts sodium, magnesium and aluminium with…
  40. Compare6 marksChallengeThe elements sodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine and argon are in Period 3 of the Periodic Table. Their melting points vary considerably across the period. Phosphorus exists as P4…
  41. Suggest6 marksChallengeAluminium hydroxide is described as amphoteric. Suggest, with equations, how aluminium hydroxide reacts with aqueous sodium hydroxide, and explain why this reaction occurs.
  42. Suggest5 marksChallengeThe chlorides of the elements across Period 3 react with water in different ways. Suggest, in terms of structure and bonding, why the reaction of SiCl4 with water produces an acidic solution, whereas the reaction of…
  43. Describe5 marksChallengeThe table shows the atomic radii of the Period 3 elements Na to Ar. Element Na Mg Al Si P S Cl Ar Atomic radius / nm 0.186 0.160 0.143 0.117 0.110 0.104 0.099 0.098 Describe and explain the general trend in atomic…
  44. Describe7 marksChallengeElement X is a member of Group 15 of the Periodic Table with atomic number 115. Using your knowledge of chemical periodicity, describe the following expected properties of element X: (a) its physical state at room…
  45. Describe7 marksChallengeThe melting points of the elements sodium, magnesium, aluminium, silicon, phosphorus and sulfur are shown. element melting point / K sodium 371 magnesium 922 aluminium 933 silicon 1687 phosphorus 317 sulfur 388…