9.2. Periodicity of chemical properties of the elements in Period 3
A subsection of Chemistry, 9701, through 9. The Periodic Table: chemical periodicity
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Explain why transition elements have variable oxidation states. Sketch the shape of a 3dxy orbital. z x y  Explain why transition elements form coloured compounds. Aqueous solutions of copper(salts contain [Cu(H2O)6]2+ ions. Equilibrium3 and equilibrium4 show two reactions of these ions. equilibrium 3 [Cu(H2O)6]2++ 2OH–Cu(OH)2+ 6H2Oequilibrium 4 [Cu(H2O)6]2++ 4NH3[Cu(NH3)4(H2O)2]2++ 4H2OState the colour of Cu(OH)2and [Cu(NH3)4(H2O)2]2+. colour of Cu(OH)2colour of [Cu(NH3)4(H2O)2]2+ Use Le Chatelier’s principle to explain why a precipitate is formed when NaOHis added dropwise to [Cu(H2O)6]2+. There are two possible stereoisomers with the formula [Cu(NH3)4(H2O)2]2+. Draw three-dimensional diagrams to show the two stereoisomers. Cu Cu  
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THEORY
2022
Paper 4, Variant 2
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The reaction of pure aluminium is only observed if the aluminium oxide layer is removed first. When pure aluminium is added to cold water, bubbles of gas are seen. State one property of aluminium oxide that explains why an aluminium object does not react with cold water until the aluminium oxide layer is removed. Write an equation, with state symbols, for the reaction of aluminium oxide with an excess of NaOH. Name one other Period 3 element that also produces bubbles of gas when added to cold water. Aluminium nitrate is a white soluble salt. On heating aluminium nitrate, thermal decomposition occurs and a brown gas is seen. State the formula of the salt of another element in Period 3 which also decomposes on heating to produce a brown gas. Aluminium chloride and phosphorus chloride are both white solids. State the maximum oxidation number of aluminium and of phosphorus in these solid chloride salts. maximum oxidation number of aluminium maximum oxidation number of phosphorus State why the maximum oxidation number of aluminium is different from that of phosphorus. Write an equation for the reaction of solid phosphorus chloride and excess water. Name the type of reaction that occurs when aluminium chloride is added to water. Explain why the solution produced after aluminium chloride is added to water has a pH of 1–2.
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THEORY
2023
Paper 2, Variant 3
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Sulfur chloride, SCl 2, is a liquid at room temperature. When SCl 2 is added to water, misty fumes are seen and a solution is made that turns universal indicator red. Identify the type of reaction that occurs when SCl 2 is added to water. Name a chloride of a different Period 3 element that is also a liquid at room temperature and produces misty fumes when added to water. A molecule of SCl 2 contains two S–Cl covalent bonds. Complete the dot-and-cross diagram in to show the arrangement of the outer electrons in a molecule of SCl 2. Use × to show electrons from the chlorine atoms. Use ● to show electrons from the sulfur atom. Cl Cl S Predict the shape of, and bond angle in, a molecule of SCl 2 by using VSEPR theory. shape bond angle Solid magnesium nitride, Mg3N2, is a crystalline solid. Deduce the oxidation numbers of magnesium and nitrogen in magnesium nitride to complete Table 2.1. Table 2.1 oxidation number in Mg3N2 magnesium nitrogen Magnesium nitride reacts with an excess of water to produce ammonia and magnesium hydroxide only. Construct an equation to describe this reaction. Explain why the solution produced in the reaction in has a pH greater than 7. Refer to the products of the reaction in your answer. Boron nitride is a white solid that melts above 2900 °C. shows part of the lattice structure of a crystal of boron nitride. boron atom nitrogen atom van der Waals’ forces covalent bond Use to deduce the empirical formula of boron nitride. Suggest the identity of another crystalline solid that has atoms arranged in layers similar to that of solid boron nitride.
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THEORY
2024
Paper 2, Variant 1
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Complete Table 1.1 using relevant information from the Periodic Table. Table 1.1 nucleon number proton number number of electrons Mg2+ Al 3+ State and explain the difference in the ionic radius of Al 3+ compared to Mg2+. Draw a labelled diagram to show the structure and bonding in sodium. shows the variation in melting point of some Period 3 elements in their standard states at room temperature and pressure. Na Mg Al Si element melting point / K P S Cl Explain why Si has a high melting point. Complete to show the variation in the melting points of the elements P, S and Cl. Two Period 3 elements react with an excess of oxygen at room pressure. Complete Table 1.2. Table 1.2 Period 3 element state of oxide at room temperature and pressure approximate pH of solution made when oxide is added to water Na S The solutions made in column 3 of Table 1.2 are mixed together. Name the type of reaction that occurs. Write an equation to describe the reaction between P4O10 and an excess of water. Aluminium hydroxide is amphoteric. Explain what is meant by amphoteric. Write an equation to describe the reaction that occurs when aluminium hydroxide, Al (OH)3, reacts with NaOH. , ,
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THEORY
2024
Paper 2, Variant 2
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This question refers to the elements shown in the Periodic Table below. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr From the elements shown, identify in each case one element that has the property described. Give the name or formula of the element. An element that has a molecule which contains only one atom. An element that has a molecule which contains only four atoms. The element that has the largest atomic radius. The element that is a liquid at room temperature and pressure. The element in Period 3 (Na to Ar) that has the highest melting point. The element in Period 3 (Na to Ar) that forms the largest anion. Use the elements shown opposite to answer the following questions. Give the formulae of two acidic oxides formed by the same element. and Give the name or formula of an oxide that is amphoteric. Identify an element whose oxide dissolves readily in water to give a strongly alkaline solution. Identify an element in Period 3 (Na to Ar) whose chloride dissolves in water to give a neutral solution. Identify an element that reacts with water to give a solution that can behave as an oxidising agent.
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THEORY
2006
Paper 2, Variant 0
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Use This question concerns the chlorides of the elements sodium to phosphorus of the third period of the Periodic Table. The melting points of these chlorides are given below. compound sodium chloride magnesium chloride aluminium chloride silicon tetrachloride phosphorus(chloride melting point/K 451* *sublimes at 451 K Give the equation, with state symbols, for the reaction of phosphorus with chlorine to form phosphorus(chloride, PCl5. Suggest, in terms of the structure and bonding, explanations for the following. You should draw diagrams where you think they will help your answer. the high melting point of sodium chloride the low melting point of silicon tetrachloride Examiner’s Use Write an equation for the reaction of silicon tetrachloride with water. What is the pH of the solution formed when each of the following compounds is dissolved in water? NaCl PCl5 When solid aluminium chloride is heated above 451 K, a vapour is formed which has Mr = 267. When this vapour is heated above 1100 K, the vapour has Mr = 133.5. What are the molecular formulae of these two forms of aluminium chloride? at 460 K at 1150 K Draw a ‘dot-and-cross’ diagram of the form of aluminium chloride that exists at the higher temperature. Draw a displayed formula of the form of aluminium chloride that exists at the lower temperature. Indicate clearly the different types of bonds present.
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THEORY
2007
Paper 2, Variant 0
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