Atomic structure and the Periodic Table — Paper 4 · IGCSE Sciences - Co-ordinated (Double) 0654

9 Magnesium is an element in Group II of the Periodic Table. (a) (i) An atom of magnesium has a mass (nucleon) number of 26. State the names and numbers of particles contained in the nucleus of this magnesium atom. … … [2] (ii) State the electronic structure of a magnesium atom. … [1] (b) Fig. 9.1 shows apparatus that a student uses to investigate the energy change when magnesium reacts with dilute hydrochloric acid. thermometer lid insulated dilute hydrochloric container acid magnesium Fig. 9.1 Fig. 9.2 shows a graph of the temperature measurements the student obtains during the investigation. BB CC temperature A 0 time Fig. 9.2 (i) Name the gas released in the reaction. … [1] (ii) Predict two ways in which the composition of the reaction mixture inside the insulated container changes during the reaction. 1 … 2 … [2] (iii) Use Fig. 9.2 to compare the average kinetic energies of the particles in the reaction mixture at points A and B, … … at points B and C. … … [1] (c) The student then investigates how the concentration of acid affects the rate of reaction between magnesium and dilute hydrochloric acid. Fig. 9.3 shows the apparatus he uses. test-tube thermometer gas syringe 50 100 excess dilute hydrochloric acid magnesium water at 20 ºC Fig. 9.3 (i) The student repeats this experiment several times using different concentrations of acid. Explain why the test-tube in Fig. 9.3 is placed in a large volume of water at 20 °C. … … … … [2] (ii) State and explain, in terms of collisions between reacting particles, the effect of an increase in acid concentration on the rate of reaction. effect … explanation … … … [2]

11 marks

Mark scheme: 9(a)(i) 12 protons ; 14 neutrons ; 2 9(a)(ii) 2,8,2 ; 1 9(b)(i) hydrogen ; 1 9(b)(ii) (concentration of) acid decreases ; (concentration of) magnesium chloride increases ; (mass of) magnesium decreases ; max 2 9(b)(iii) K.E. higher at B than at A AND K.E. at B and C the same ; 1 9(c)(i) reaction releases thermal energy / temperature of mixture increases / exothermic / temperature affects rate ; water (seeks to) keep temperature constant ; 2 9(c)(ii) reaction rate increases ; increased collision frequency ; 2

This question in 0654/41 May/June 2017

2 Fig. 2.1 shows the electronic structures of atoms of four elements, A, B, C and D. These letters are not the chemical symbols of the elements. A B x x x x x x x x x x x x x x x C D x x x x x x x x x x x x x x x x x x x x x x x x x x x Fig. 2.1 (a) (i) State the letters of the elements that are good conductors of electricity. Use the information in Fig. 2.1 to explain your answer. elements … explanation … … [3] (ii) State the letter of the least reactive element. Use the information in Fig. 2.1 to explain your answer. element … explanation … … [2] (iii) Elements B and C in Fig. 2.1 react together to form a compound. State the type of chemical bonding in this compound. Explain your answer in terms of the type of elements involved. type of bonding … explanation … … [2] (b) Bronze is an alloy of copper and tin. Bronze is harder (less malleable) than either of these two pure metals. Fig. 2.2 shows the arrangement of atoms in bronze. tin atom copper atom Fig. 2.2 Explain the difference in hardness between bronze and copper. … … … … … [2]

9 marks

Mark scheme: 2(a)(i) A and B ; from Groups I and II / have only 1 or 2 electrons in outer shell ; are metals / have metallic properties ; 3 2(a)(ii) D ; complete outer shell / is a noble gas / is very stable / does not need to bond / does not need, to gain / lose / share electrons ; 2 2(a)(iii) ionic / electrovalent ; metal bonding with non-metal ; 2 2(b) arrangement of atoms in bronze is less regular / disrupted by atoms of different size ; layers of atoms slide more easily in copper / do not slide so easily in bronze ; 2

This question in 0654/42 May/June 2017

2 Fig. 2.1 shows part of the Periodic Table. I II III IV V VI VII VIII 1 2 H He 6 8 C O 11 12 Na Mg Fig. 2.1 (a) State the number of elements in the first period of the Periodic Table. … [1] (b) The atomic number of magnesium is 12. (i) Define the term atomic (proton) number. … … … [2] (ii) A sodium atom is 23 times heavier than a hydrogen atom. Explain this statement in terms of atomic structure. … … … [2] (c) The electronic structure of a carbon atom is 2,4. State the electronic structure of a magnesium atom. … [1] (d) Sodium is produced industrially using electrolysis. Fig. 2.2 shows a diagram of the process. molten sodium floating on the gas G electrolyte molten electrolyte containing sodium chloride – + cathode anode Fig. 2.2 State the name and chemical formula of gas G. name … chemical formula … [2]

8 marks

Mark scheme: 2(a) 2 ; 1 2(b)(i) number of protons ; in one atom (of an element) / in the nucleus ; 2 2(b)(ii) mass number of sodium is 23 and mass number of hydrogen is 1; sodium (nucleus) contains neutrons and protons ; protons and neutrons have same mass ; 12 (neutrons) and 11 (protons) and hydrogen has 1 proton ; max 2 2(c) 2,8,2 ; 1 2(d) chlorine ; Cl2 ; 2

This question in 0654/41 Oct/Nov 2017

2 Table 2.1 shows the numbers of neutrons and the electronic structures in atoms of four elements W, X, Y and Z. Table 2.1 element number of neutrons electronic structure W 8 2,6 X 16 2,8,6 Y 18 2,8,7 Z 22 2,8,8 (a) (i) Using the information in Table 2.1, state which of these elements are in the same group of the Periodic Table. Explain your answer. elements … explanation … … [1] (ii) Deduce the atomic number of element Y. … [1] (iii) Deduce the relative atomic mass of element X. Explain your answer. relative atomic mass … explanation … … [2] (iv) Predict and explain whether there are many compounds that contain element Z. … … … [2] (b) Fig. 2.1 shows the structure of a molecule formed when atoms of W and Y in Table 2.1 combine. Y W Y Fig. 2.1 Complete Fig. 2.2 to show how all the outer-shell electrons are arranged in this molecule. Use information about the electronic structures of elements W and Y in Table 2.1 to help you. Y W Y Fig. 2.2 [3]

9 marks

Mark scheme: 2(a)(i) W and X AND same outer electron number ; 1 2(a)(ii) 17 ; 1 2(a)(iii) 32 ; number of electrons = number of protons / relative atomic mass OR mass number = protons + neutrons / 16 + 16 / it is S ; 2 2(a)(iv) (no) Z has a complete outer shell ; so atoms are stable / inert / do not react / do not form chemical bonds / noble gas ; 2 2(b) two shared pairs showing the covalent bonds ; four non-bonding electrons on W ; six non-bonding electrons on both Y atoms ; 3

This question in 0654/43 Oct/Nov 2017

5 Iodine is an element in Group VII of the Periodic Table. A copy of the Periodic Table is shown on page 28. (a) Describe the trend in the physical state of the elements chlorine, fluorine, bromine and iodine at room temperature (20 °C). … … … [2] (b) State the number of electrons in the outer shell of an iodine atom. Explain your answer. number of electrons … explanation … … [2] (c) Seawater contains iodide ions, I−. (i) Explain, in terms of protons and electrons, why an iodine atom is neutral but an iodide ion has an electrical charge of −1. … … … [2] (ii) Iodine can be produced by passing chlorine through seawater. Complete the balanced ionic equation for the reaction producing iodine. Cl + … I− … + … [2] 2 (d) Fig. 5.1 shows apparatus used to electrolyse aqueous potassium iodide, KI. d.c. power supply – + switch aqueous potassium iodide Fig. 5.1 When the switch is closed, a colourless gas is produced at the cathode. Iodine is produced at the anode. (i) Identify the colourless gas. … [1] (ii) Use ideas about atoms, ions and the transfer of electrons to explain the formation of iodine during the electrolysis of aqueous potassium iodide. … … … [2]

11 marks

Mark scheme: 5(a) gas to liquid ; liquid to solid ; 2 5(b) 7 ; outer electron number = group number ; 2 5(c)(i) in the atom, number of protons = number of electrons / positive and negative charge is balanced ; in the ion, electrons exceed protons by one / owtte ; 2 5(c)(ii) (Cl2 +) 2(I–) → 2Cl– + I2 2I– and I2 ; 2Cl– ; 2 5(d)(i) hydrogen ; 1 5(d)(ii) one electron moves from ion (to anode / positive electrode) ; (iodide) ions attracted / move to anode OR (iodide) ions become iodine atoms OR (iodine) atoms form (iodine) molecules ; 2

This question in 0654/41 Oct/Nov 2018

8 Fig. 8.1 shows part of Group I of the Periodic Table. 3 Li lithium 7 11 Na sodium 23 19 K potassium 39 37 Rb rubidium 85 Fig. 8.1 (a) (i) State the electronic structure of a sodium atom. … [1] (ii) Describe how the electronic structure of sodium is related to its group number. … … [1] (b) A teacher adds Universal Indicator solution to water in a large bowl. She places a piece of sodium onto the surface of the water. Fig. 8.2 shows the apparatus she uses. sodium water containing Universal Indicator Fig. 8.2 Students notice that gas forms around the sodium and the indicator changes colour. (i) The teacher informs her students that hydrogen and sodium hydroxide are formed by the reaction. State and explain the change in colour of the indicator. change in colour … explanation … … [2] (ii) Suggest one similarity and one difference between rubidium and sodium in their reaction with water containing Universal Indicator. Explain your answers. similarity … explanation … difference … explanation … [3] (c) Fig. 8.3 shows an incomplete diagram of part of the structure of a sodium chloride crystal. Complete the diagram by showing the arrangement of sodium ions, Na+, and chloride ions, Cl –. Cl – (ions are not drawn to scale) Fig. 8.3 [2] [Total: 9]

9 marks

Mark scheme: 8(a)(i) 2, 8, 1 ; 1 8(a)(ii) number of valence / outer shell, electrons equals group number or sodium has 1 outer electron so is in group 1 ; 1 8(b)(i) green to blue / violet ; (sodium hydroxide is) alkaline / pH increases / pH becomes >7 ; 2 8(b)(ii) similarity and difference: hydrogen / hydroxide / alkali also formed and more vigorous reaction ; similarity explanation: elements in same group have similar properties ; or same number/one electron in outer shell (so react similarly) ; difference explanation: trend to greater reactivity down Group I ; or outer electron more easily lost/further from nucleus (so more reactive) ; 3 8(c) Na+ and Cl – in equal numbers (+1Cl– ); alternating in both directions ; 2

This question in 0654/43 May/June 2019

2 (a) Table 2.1 shows some information about the structure of atoms. Complete Table 2.1. [2] Table 2.1 particle charge relative mass electron … … neutron 1 … proton +1 … (b) There are two isotopes of bromine. One isotope is called bromine-79 and the other is called bromine-81. (i) Table 2.2 shows some information about one atom of each isotope of bromine. Complete Table 2.2. [2] Table 2.2 number of number of number of symbol protons neutrons electrons bromine-79 79 35 44 35 35Br bromine-81 … … … … (ii) The two isotopes of bromine have the same chemical properties. Explain why. … … [1] (c) Sodium is a metal. Bromine is a non-metal. Sodium reacts with bromine to form sodium bromide. Sodium bromide is an ionic compound. (i) Describe how metallic elements and non-metallic elements form ionic bonds. … … … … [3] (ii) Explain why bromine, Br2, has a low melting point. … … … [2] [Total: 10]

10 marks

Mark scheme: 2(a) particle charge relative mass electron –1 0.0005 / negligible / 1 ÷ 1835 neutron 0 / no charge 1 proton +1 1 ;; 1 mark for each correct column 2 2(b)(i) symbol – 81 35Br ; protons 35, neutrons 46, electrons 35 ; 2 Question Answer Marks 2(b)(ii) (isotopes have the same properties because) they (both) have the same number of electrons in the outer shell / they (both) have seven electrons in the outer shell ; 1 2(c)(i) metallic elements lose electrons to form positive ions ; non-metallic elements gain electrons to form negative ions ; (there is a) strong attraction between (oppositely charged) ions ; (because of) their opposite (electrical) charges ; max 3 2(c)(ii) bromine is covalent ; weak attractive forces (between molecules) ; 2

This question in 0654/41 May/June 2020

2 Atoms contain protons, neutrons and electrons. (a) Complete Table 2.1 about protons, neutrons and electrons. Table 2.1 relative charge relative mass location in an atom protons in nucleus … … neutrons 1 … … electrons –1 … … [3] (b) Fig. 2.1 shows the structure of an atom of nitrogen. N Fig. 2.1 (i) Write the electronic structure for a nitrogen atom. … [1] (ii) Nitrogen is in Group V of the Periodic Table. State how Fig. 2.1 shows that nitrogen is in Group V. … [1] (c) Nitrogen atoms bond together to form nitrogen molecules, N2. Draw a dot-and-cross diagram to show the bonding in a nitrogen molecule. Show only the outer shell electrons. [2] (d) Nitrogen is one of the gases found in clean air. Complete Table 2.2 about the gases in clean air. Table 2.2 percentage (%) in gas clean air carbon dioxide 0.041 oxygen … nitrogen … varies … [3] (e) Nitrogen monoxide gas, NO, is an air pollutant. A catalytic converter removes nitrogen monoxide from car exhaust gases. Write a balanced symbol equation for this reaction. … [2] [Total: 12]

12 marks

Mark scheme: 2(a) relative charge relative mass location in an atom protons +1 / + 1 (in nucleus) neutrons 0 / no charge / neutral (1) in nucleus electrons (–1) almost 0 / negligible / 1÷1850 in shells / orbits around nucleus ;;; 3 2(b)(i) 2, 5 ; 1 2(b)(ii) (nitrogen has) five electrons in the outer shell ; 1 Question Answer Marks 2(c) ;; 2 2(d) gas percentage in clean air (%) carbon dioxide 0.035 oxygen 21 nitrogen 78 (named) noble gases / water (vapour) varies ;;; 3 2(e) 2CO + 2NO → N2 + 2CO2 / 2NO → N2 + O2 ;; 2

This question in 0654/42 Oct/Nov 2020

5 (a) Look at the list of atomic symbols. Br Cu K Mg N Ne Zn Answer the following questions choosing from the list of atomic symbols. Each symbol can be used once, more than once or not at all. (i) State the symbol for an element with a full outer shell of electrons. … [1] (ii) State the symbol of the element with the electronic structure 2,8,2. … [1] (iii) State the symbols of two elements that form basic oxides. … and … [1] (b) The symbol of an isotope of oxygen is 188O. Fig. 5.1 shows the nucleus of an atom of 188O. Fig. 5.1 State the name of the particle shown by (i) … [1] (ii) … [1] (iii) Draw a similar diagram to Fig. 5.1 to show a different isotope of oxygen. [1] (c) Fig. 5.2 shows the electronic structures of a lithium atom and of a chlorine atom. lithium atom chlorine atom Fig. 5.2 When lithium reacts with chlorine a lithium ion and a chloride ion are made. Draw dot-and-cross diagrams to show the electronic structures of a lithium ion and of a chloride ion. Include the charge on each ion. lithium ion chloride ion [2] [Total: 8]

8 marks

Mark scheme: 5(a)(i) Ne ; 1 5(a)(ii) Mg ; 1 5(a)(iii) any two from Cu, Zn, K, Mg ;; 1 Question Answer Marks 5(b)(i) proton ; 1 5(b)(ii) neutron ; 1 5(b)(iii) diagram with 8 protons and any number of neutrons other than 10; 1 5(c) lithium ion ; chloride ion ; 2

This question in 0654/43 Oct/Nov 2020

2 (a) Table 2.1 shows some information about the charges and relative masses of three subatomic particles. Table 2.1 particle A particle B particle C charge +1 no charge –1 1 relative mass 1 1 1840 Use the information in Table 2.1 to state the names of particles A, B and C. particle A … particle B … particle C … [3] (b) Fig. 2.1 shows a diagram of an atom of magnesium. – – – nucleus – 12 protons – – – – 12 neutrons – – – – Fig. 2.1 (i) State why this atom of magnesium has a proton number (atomic number) of 12 and a nucleon number (mass number) of 24. proton number of 12 because … … nucleon number of 24 because … … [2] (ii) State the electronic structure of this atom of magnesium. … [1] (c) Magnesium reacts with oxygen to form magnesium oxide, MgO. Magnesium oxide is an ionic compound with a melting point of 2852 °C. Oxygen reacts with hydrogen to form water, H2O. Water is a covalent compound with a melting point of 0 °C. Explain the difference in the melting points of magnesium oxide and water in terms of attractive forces. … … … … [3] (d) Magnesium oxide reacts with dilute hydrochloric acid, HCl. Magnesium chloride, MgCl 2, is made. The balanced symbol equation for the reaction is shown. MgO + 2HCl MgCl 2 + H2O In an experiment, 2.0 g of magnesium oxide reacts with excess dilute hydrochloric acid. Calculate the maximum mass of magnesium chloride that can be made. Show your working. [Ar : Cl , 35.5; H, 1; Mg, 24; O, 16] mass of magnesium chloride = … g [2] [Total: 11]

11 marks

Mark scheme: 2(a) (particle A) – proton ; (particle B) – neutron ; (particle C) – electron ; 3 2(b)(i) proton number of 12 because (magnesium) has 12 protons ; nucleon number of 24 because (magnesium) has 12 protons and 12 neutrons ; 2 2(b)(ii) 2.8.2 ; 1 Question Answer Marks 2(c) magnesium oxide has strong (electrostatic) forces of attraction between oppositely charged magnesium ions and oxide ions ; water has weak intermolecular forces / weak attraction between (water) molecules ; strong (electrostatic) forces of attraction take more energy to break than weak intermolecular forces / ORA ; 3 2(d) relative molecular mass of MgO = 40 and of MgCl2 = 95 ; × 2.0 95 40 or 95 20 = 4.75 (g) ; 2

This question in 0654/42 Feb/March 2021

5 An atom of chlorine has a proton number (atomic number) of 17 and a nucleon number (mass number) of 37. (a) (i) Complete Table 5.1 to show the numbers of protons, neutrons and electrons in this atom of chlorine. Table 5.1 particle number proton … neutron … electron … [3] (ii) Chlorine is in Group VII of the Periodic Table. State what information this gives about the number of electrons in the outer shell of a chlorine atom. … [1] (iii) Chlorine exists as isotopes. Explain what is meant by the term isotopes. … … … [2] (b) Chlorine atoms bond together to form the covalent molecule, Cl2. Chlorine, Cl2, is a gas at room temperature. Chlorine atoms bond with sodium atoms to form the ionic compound sodium chloride, NaCl. Sodium chloride, NaCl, is a solid at room temperature. Explain why chlorine is a gas but sodium chloride is a solid at room temperature in terms of attractive forces. … … … … [3] (c) Chlorine reacts with sodium bromide, NaBr. Write the balanced symbol equation for this reaction. … [2] [Total: 11]

11 marks

Mark scheme: 5(a)(i) particle number proton 17 neutron 20 electron 17 3 5(a)(ii) (chlorine has) 7 (electrons in the outer shell) ; 1 5(a)(iii) (atoms with) same proton or atomic number / same number of protons ; different nucleon or mass number / different number of neutrons ; 2 5(b) sodium chloride has strong (electrostatic) forces of attraction between (oppositely charged) ions ; chlorine has weak intermolecular forces / weak attractions between (chlorine) molecules ; strong (electrostatic) forces of attraction take more energy to break than weak intermolecular forces / ORA ; 3 5(c) Cl2 + 2NaBr → Br2 + 2NaCl correct formulae ; then correct balancing ; 2

This question in 0654/41 May/June 2021

11 (a) Table 11.1 shows some information about particles found in an atom. Complete Table 11.1. Table 11.1 particle relative mass relative charge 1 electron 1840 … neutron 0 … proton 1 … [3] (b) The diagrams in Fig. 11.1 each show the nucleus of a different atom. key neutron proton atom A atom B atom C atom D atom E Fig. 11.1 (i) State which atom has a proton number (atomic number) of 3. … [1] (ii) State which atom has a nucleon number (mass number) of 6. … [1] (iii) State which two atoms are isotopes of the same element. … and … [1] [Total: 6]

6 marks

Mark scheme: 11(a) particle relative mass relative charge electron 1 1840 –1 / – / negative neutron 1 0 proton 1 +1 / + / positive ;;; 3 11(b)(i) C ; 1 11(b)(ii) C ; 1 11(b)(iii) D and E ; 1

This question in 0654/42 May/June 2021

11 Fig. 11.1 shows an outline of the Periodic Table. H He C O F Al Ar K Cu Br Sr Fig. 11.1 (a) Draw a line to link each element to its correct description. Use each description only once. element description an element with 8 electrons in its outer shell He an element with an electronic structure of 2 Al an element in Group 3 and Period 3 Ar an element in Group 6 and Period 3 [3] (b) Argon is a gas used in lamps. Explain why. … [1] (c) The nucleus of a carbon atom contains six protons. State the charge on a proton. … [1] (d) Potassium metal reacts with the non-metal bromine to form potassium bromide. Potassium bromide is an ionic compound. Describe how metallic and non-metallic elements form ionic bonds. … … … … [3] (e) The electronic structure of carbon is 2.4. The electronic structure of oxygen is 2.6. The atoms in a molecule of carbon dioxide, CO2, are held together by covalent bonds. Draw the dot-and-cross diagram to show the bonding in carbon dioxide. You only need to include the outer shell electrons. [2] [Total: 10]

10 marks

Mark scheme: 11(a) ;;; 11(b) (argon is) inert / unreactive ; 1 11(c) + / +1 / positive ; 1 11(d) metal (atoms) lose electrons ; non-metal (atoms) gain electrons ; metal (atoms) form positive ions and non-metal (atoms) form negative ions ; attraction between (oppositely charged) ions ; max 3 3 11(e) 2

This question in 0654/43 May/June 2021

11 (a) This is the information given on the Periodic Table about an atom of iron. 56 26 Fe Complete Table 11.1 to show the numbers of protons and neutrons in this iron atom. Table 11.1 particle number protons … neutrons … electrons 26 [2] (b) Iron metal corrodes. Stainless steel is an alloy made from iron and chromium. Describe one difference in the properties of the alloy stainless steel and the metal iron. … … [1] (c) Iron pyrites is an ionic compound. Fig. 11.1 shows a structure for iron pyrites. Key Fe S Fig. 11.1 Determine the formula of iron pyrites using Fig. 11.1. formula = … [1] (d) Iron metal reacts with the non-metal oxygen to form iron oxide. Iron oxide is an ionic compound. Describe how metallic and non-metallic elements form ionic bonds. … … … … [3] (e) Iron is extracted from iron oxide by reduction with carbon. Explain why carbon can be used to extract iron from iron oxide. … … … [2] [Total: 9]

9 marks

Mark scheme: 11(a) particle number protons 26 ; neutrons 30 ; electrons 26 2 11(b) (stainless steel) is more resistant to corrosion ; 1 11(c) FeS2 ; 1 11(d) metal (atoms) lose electrons and non-metal (atoms) gain electrons ; metal (atoms) form positive ions and non-metal (atoms) form negative ions ; attraction between oppositely charged ions ; 3 11(e) carbon is more reactive than iron / ORA ; carbon displaces iron / carbon removes oxygen (from iron oxide) ; 2

This question in 0654/41 Oct/Nov 2021

11 (a) An oxygen atom has the electronic structure 2,6. Use the electronic structure to explain which group of the Periodic Table oxygen is in. … … [2] (b) Sodium forms an ionic compound with oxygen. State the formulae of a sodium ion and an oxide ion. Use the formulae of the ions to determine the formula of the ionic compound sodium oxide. formula of a sodium ion … formula of an oxide ion … formula of sodium oxide … [3] (c) Oxygen can also form covalent bonds. Complete the dot-and-cross diagram to show the covalent bonding in a molecule of carbon dioxide. You only need to include the outer shell electrons. O C O [3] (d) Covalent compounds, such as carbon dioxide, have low melting points. State which letter, A, B, C or D, in Table 11.1 gives the correct explanation for why most covalent compounds have low melting points. Table 11.1 explanation A covalent bonds are strong B covalent bonds are weak C electrons are free to move D weak intermolecular forces of attraction … [1] (e) Calculate the relative molecular mass, Mr, of aluminium sulfate, Al2SO4. Show your working. [Ar: Al, 27; O, 16; S, 32] relative molecular mass = … [2] [Total: 11]

11 marks

Mark scheme: 11(a) group VI / group 6 ; (because) 6 electrons in the outer shell ; 2 11(b) sodium ion – Na+ ; oxide ion – O2- ; sodium oxide – Na2O ; 3 11(c) ;;; 3 11(d) D ; 1 11(e) [2 × 27] + 32 + [4 × 16] ; = 150 ; 2

This question in 0654/42 Oct/Nov 2021

5 (a) Table 5.1 shows some information about particles found in atoms. Complete Table 5.1. Table 5.1 particle relative mass charge electron … … proton +1 … neutron 1 … [2] (b) Fig. 5.1 shows a sodium atom. electron nucleus Fig. 5.1 (i) A sodium atom, Na, can form a sodium ion, Na+. Describe how a sodium atom forms a sodium ion. … [1] (ii) Write a balanced ionic half equation to show how a sodium atom forms a sodium ion. Use e– to represent an electron. … [1] (c) Table 5.2 gives some information about three halogens. Complete Table 5.2. Table 5.2 halogen atomic number electronic structure fluorine 9 … chlorine 17 2.8.7 bromine 2.8.18.7 … [2] (d) Sodium, Na, reacts with chlorine, Cl 2, to make sodium chloride, NaCl. (i) Construct the balanced symbol equation for this reaction. … [2] (ii) Sodium chloride, NaCl, is an ionic compound. Draw a dot‑and‑cross diagram to show the bonding in sodium chloride. Include the charges on the ions. [2] [Total: 10]

10 marks

Mark scheme: 5(a) particle relative mass relative charge electron almost 0 or negligible or 1 / 1850 or 1 / 1836 –1 proton 1 +1 neutron 1 0 or no charge ;; 2 5(b)(i) loses one electron / owtte ; 1 5(b)(ii) Na  Na+ + e– ; 1 Question Answer Marks 5(c) halogen atomic number electronic structure fluorine 9 2.7 ; chlorine 17 2.8.7 bromine 35 ; 2.8.18.7 2 5(d)(i) 2Na + Cl2  2 NaCl ;; 2 5(d)(ii) ;; 2

This question in 0654/42 May/June 2022

2 (a) Fig. 2.1 shows the atoms of some elements. The letters do not represent the symbols of the elements. A B C D E Fig. 2.1 (i) State the evidence from Fig. 2.1 that shows that element C is in Group III of the Periodic Table. … [1] (ii) Identify which of the elements in Fig. 2.1 forms an ion with a charge of –3. Choose from A, B, C, D or E. answer = … [1] (iii) Write the electronic structure of element E. … [1] (iv) Identify which of the elements in Fig. 2.1 has a proton number (atomic number) of 9. Choose from A, B, C, D or E. answer = … [1] (v) State the evidence from Fig. 2.1 that shows that element A is unreactive. … [1] (vi) Elements B and D react together to form an ionic compound. Draw a dot-and-cross diagram to show the ions formed when elements B and D react together. Include the charges on the ions. [2] (vii) Ionic compounds have a lattice structure. Describe the lattice structure of ionic compounds. … … … [2] (b) The nucleus of an atom contains protons and neutrons. Table 2.1 shows the relative charge and relative mass of a proton. Complete the table to show the relative charge and relative mass of a neutron. Table 2.1 relative charge relative mass proton +1 1 neutron [2] [Total: 11]

11 marks

Mark scheme: 2(a)(i) (element C) has 3 electrons in the outer shell ; 1 2(a)(ii) E ; 1 2(a)(iii) 2.8.5 ; 1 2(a)(iv) D ; 1 2(a)(v) (Element A) has a fu ll outer shell ; 1 2(a)(vi) 2 D B ;; 2(a)(vii) regular / alternating, arrangement ; 2 of positive and negative ions ; 2(b) 2 relative charge relative mass proton +1 1 neutron 0 / no charge / neutral ; 1;

This question in 0654/42 Oct/Nov 2022

5 This question is about metals. (a) Potassium is a metal in Group I of the Periodic Table. Fig. 5.1 shows the electronic structure of three elements. A B C Fig. 5.1 (i) State which diagram A, B or C, shows the electronic structure of a Group I metal. … [1] (ii) A student wants to confirm that a compound contains potassium. The student uses a flame test. State what the student observes if the compound contains potassium. … [1] (b) Iron is a transition element. Iron(II) sulfate contains iron(II) ions, Fe2+. Sodium hydroxide solution is used to test for iron(II) ions. The iron(II) ions react with OH– ions from the sodium hydroxide solution. A precipitate of iron(II) hydroxide, Fe(OH)2, is made. (i) State the colour of the precipitate of iron(II) hydroxide. … [1] (ii) Construct the balanced ionic equation for the formation of Fe(OH)2. Include state symbols. … [2] (c) Magnesium reacts with oxygen to make magnesium oxide. (i) Fig. 5.2 shows the electronic structure of a magnesium atom. The proton number (atomic number) of magnesium is 12. Fig. 5.2 Draw a diagram to show the electronic structure of an oxygen atom. The proton number (atomic number) of oxygen is 8. [1] (ii) When magnesium reacts with oxygen, magnesium ions and oxide ions are made. Fig. 5.3 shows the electronic structure of an oxide ion. 2– Fig. 5.3 Draw a diagram to show the electronic structure of a magnesium ion. [2] (iii) Explain why magnesium oxide has a high melting point. … … … [2] (d) Potassium oxide is also an ionic compound. Potassium ions, K+, combine with oxide ions, O2–, to form potassium oxide. Determine the formula of potassium oxide. … [1] [Total: 11]

11 marks

Mark scheme: 5(a)(i) B ; 1 5(a)(ii) lilac / purple, (flame) ; 1 5(b)(i) green ; 1 5(b)(ii) Fe2+(aq) + 2OH– (aq) → Fe(OH)2 (s) ;; 2 5(c)(i) 1 ; 5(c)(ii) 2 ;; 5(c)(iii) strong attraction between (positive and negative) ions / strong electrostatic attraction / strong ionic bond ; 2 so large amount of energy needed to overcome the attraction / owtte ; 5(d) K2O ; 1

This question in 0654/43 Oct/Nov 2022

11 Diamond is one form of carbon. (a) (i) State the name of another form of carbon. … [1] (ii) Diamond is used in cutting tools such as those shown in Fig. 11.1. Fig. 11.1 State why diamond is used. … … [1] (b) Silicon dioxide, SiO2, has a similar structure to diamond. Fig. 11.2 shows the structure of silicon dioxide. silicon atoms oxygen atoms Fig. 11.2 Describe the structure and bonding in silicon dioxide. Use Fig. 11.2 to help you. … … … [2] (c) One of the isotopes of carbon is called carbon-12 and the other is called carbon-14. Table 11.1 shows some information about carbon-12. Complete the table for carbon-14. Table 11.1 number of number of number of protons neutrons electrons carbon-12 6 6 6 carbon-14 [1] (d) Relative atomic mass, Ar , is defined in terms of a carbon atom. Complete the definition of relative atomic mass. Choose words from the list. Each word may be used once, more than once or not at all. average compound density element formula mass Relative atomic mass is the … mass of naturally occurring atoms of an … on a scale where the 12 C atom has a … of exactly 12 units. [3] (e) Calculate the number of moles in 0.6 g of carbon. [Ar : C, 12;] moles = … [1] [Total: 9]

9 marks

Mark scheme: 11(a)(i) graphite ; 1 11(a)(ii) (diamond is) hard ; 1 11(b) covalent bonding (between the atoms) ; 2 any one from: (silicon dioxide has a) macromolecular / giant structure ; each silicon atoms bonds to 4 oxygen atoms and each oxygen atom bonds to 2 silicon atoms ; 11(c) 1 number of number of number of protons neutrons electrons carbon-12 6 6 6 carbon-14 6 8 6 ; 11(d) average ; 3 element ; mass ; 11(e) (moles = 0.6 ÷ 12 =) 0.05 ; 1

This question in 0654/43 Oct/Nov 2022

5 (a) Fig. 5.1 shows a diagram of a lithium atom. nucleus containing … … and … Fig. 5.1 (i) Complete the labels on Fig. 5.1. [3] (ii) State the electronic structure of a lithium atom. … [1] (b) (i) A lithium atom bonds with a chlorine atom by ionic bonding. Fig. 5.2 shows the formation of a lithium ion, Li+, from a lithium atom. + Li Li Fig. 5.2 Draw a similar diagram to show the formation of a chloride ion, Cl –, from a chlorine atom. [2] (ii) Ionic compounds, such as lithium chloride, have a lattice structure. Describe the lattice structure of ionic compounds. You may include a labelled diagram if you wish. … … … [2] (c) (i) Carbon has three naturally occurring isotopes: carbon‑12, carbon‑13 and carbon‑14. Complete Table 5.1 to show the numbers of protons, neutrons and electrons in an atom of each isotope. Table 5.1 isotope protons neutrons electrons carbon‑12 6 6 6 carbon‑13 6 … … carbon‑14 8 … … [2] (ii) Explain, in terms of particles, why these isotopes have the same chemical properties. … … [1] [Total: 11]

11 marks

Mark scheme: 5(a)(i) (nucleus containing) protons ; (and) neutrons ; electron ; 5(a)(ii) 2.1 ; 1 5(b)(i) ;; 2 Question Answer Marks 5(b)(ii) regular arrangement ; of alternating positive and negative ions ; 2 5(c)(i) isotope protons neutrons electrons carbon-12 6 6 6 carbon-13 6 7 6 carbon-14 6 8 6 ;; 2 5(c)(ii) they have the same number of electrons in the outer shell ; 1

This question in 0654/41 May/June 2023

8 (a) Copper has two isotopes, copper‑63 and copper‑65. Table 8.1 shows information about copper‑63 and copper‑65. Complete Table 8.1. Table 8.1 proton (atomic) nucleon (mass) isotope protons neutrons electrons number number copper‑63 29 63 29 34 … copper‑65 29 65 29 … … [3] (b) Complete the sentence to describe what is meant by isotopes. Choose words from the list. compound electron element group nucleon nucleus proton Isotopes are atoms of the same … which have the same … number but a different … number. [3] (c) An element is in Group II and Period 3 of the Periodic Table. Predict the electronic structure of this element. Tick (3) one box. 2.3 2.2.3 2.8.2 2.8.3 [1] (d) Complete Fig. 8.1 to show the covalent bonding in a molecule of nitrogen, N2. N N Fig. 8.1 [2] (e) The element nitrogen is covalently bonded. The melting point of nitrogen is –210 °C. Calcium nitride, Ca3N2, is an ionic compound. The melting point of calcium nitride is 1195 °C. Explain the difference in melting points in terms of attractive forces. … … … [2] [Total: 11]

11 marks

Mark scheme: 8(a) isotope proton (atomic) number nucleon (mass) number protons neutrons electrons copper-63 29 63 29 34 29 copper-65 29 65 29 36 29 ;;; 3 8(b) element ; proton ; nucleon ; 3 Question Answer Marks 8(c) 2.8.2  ; 1 8(d) ;; 2 8(e) any two from: nitrogen / covalent molecules, has weak intermolecular forces / weak attractions between (nitrogen) molecules ; calcium nitride / ionic compounds, has strong (electrostatic) forces of attraction between oppositely charged ions ; higher melting point due to more energy required to overcome stronger forces / ORA ; 2

This question in 0654/42 May/June 2023

5 (a) Complete the sentences about the structure of an atom. An atom has a central nucleus containing … and … and a series of … of electrons surrounding the nucleus. [2] (b) The element oxygen exists as isotopes. State what is meant by isotopes. … … … … [3] (c) Oxygen atoms join together with covalent bonds to form oxygen molecules, O2. Complete the dot‑and‑cross diagram to show the bonding in an oxygen molecule. O O [2] (d) Oxygen atoms bond with silicon atoms to form silicon(IV) oxide, SiO2, which has a high melting point and is hard like diamond. Describe the way the silicon and oxygen bond in the structure of silicon(IV) oxide. … … … [2] [Total: 9]

9 marks

Mark scheme: 5(a) protons (and) neutrons 2 shells one or two correct for 1 mark three correct for 2 marks ;; 5(b) (idea of) atoms of the same / an element ; 3 which have the same proton / atomic number ; but a different nucleon / mass number ; 5(c) 2 one mark for double bond between oxygen atoms one mark for rest of structure correct ;; 5(d) any two from: 2 macromolecular / (giant) lattice ; each oxygen atom bonds with 2 silicon atoms ; each silicon atom bonds with 4 oxygen atoms ; sharing of electrons / covalent bond ;

This question in 0654/41 Oct/Nov 2024

5 Fig. 5.1 shows the structures of four carbon compounds. H H H H H C C H C C H H H H A B H H H H H C C O H C C H H H H C D Fig. 5.1 (a) (i) State which compound is ethene. Choose from A, B, C or D. … [1] (ii) State which compound is an unsaturated hydrocarbon. Choose from A, B, C or D. … [1] (iii) Compound B is made from compound D. State what type of reaction takes place. … [1] (iv) Describe how compound C is made from compound D. … … [2] (v) Compound A is a member of a homologous series. State two similarities between the members of a homologous series. 1 … 2 … [2] (b) Fig. 5.2 shows the structure of a carbon atom. 6p 6n p = proton n = neutron = electron Fig. 5.2 (i) Carbon is in Group IV of the Periodic Table. Describe how to deduce from Fig. 5.2 that carbon is in Group IV. … … [1] (ii) Carbon exists as a mixture of isotopes. Complete Fig. 5.3 to show a different isotope of carbon from that shown in Fig. 5.2. Fig. 5.3 [3] [Total: 11]

11 marks

Mark scheme: 5(a)(i) D ; 1 5(a)(ii) D ; 1 5(a)(iii) addition polymerisation ; 1 5(a)(iv) addition of steam ; 2 using a catalyst ; 5(a)(v) general formula ; 2 chemical properties ; 5(b)(i) (carbon has) 4 electrons in the outer shell ; 1 5(b)(ii) diagram showing: 3 6 protons ; 6 electrons in the correct configuration of 2.4 ; any number of neutrons other than 6 ;

This question in 0654/42 Oct/Nov 2024

8 (a) Table 8.1 shows some information about the structure of atoms. Complete Table 8.1. Table 8.1 particle charge relative mass electron –1 … neutron … … proton 1 … [2] (b) Fig. 8.1 shows two forms of the element carbon, diamond and graphite. diamond graphite Fig. 8.1 Put a tick (3) next to the correct description for the structure of diamond and graphite. giant covalent ionic polymer metallic [1] (c) Graphite is used to make electrodes for electrolysis because it is a good conductor of electricity. Explain why graphite is a good conductor of electricity. Use ideas about structure and bonding. … … … [2] (d) There are different isotopes of the element carbon. Two of the isotopes are called carbon-12 and carbon-14. (i) Table 8.2 shows some information about one atom of each of these isotopes of carbon. Complete Table 8.2. Table 8.2 number of protons number of neutrons number of electrons carbon-12 6 6 … carbon-14 … … … [2] (ii) The different isotopes of carbon have the same chemical properties. Explain why. … … [1] (e) Elements are organised in the Periodic Table in groups. Carbon is in Group IV of the Periodic Table. Another element, tellurium, is in Group VI of the Periodic Table. A common compound of tellurium is sodium telluride, Na2Te. Put a tick (3) next to the formula of the tellurium ion in sodium telluride, Na2Te. Te– Te+ Te2– Te2+ Te6– [1] [Total: 9]

9 marks

Mark scheme: 8(a) 2 particle charge relative mass electron –1 0.0005 / negligible / almost 0 / 11835 neutron 0 / no charge 1 proton +1 1 1 mark for each correct column ;; 8(b) giant covalent ; 1 8(c) (graphite has) free / delocalised electrons ; 2 which can move ; 8(d)(i) 2 number of number of number of protons neutrons electrons carbon-12 6 6 6 carbon-14 6 8 6 1 mark for each row ;; 8(d)(ii) they (both) have the same number of electrons in the outer shell / they (both) have 4 electrons in the outer shell / 1 they have the same electron(ic) structure / configuration ; 8(e) Te2– ; 1

This question in 0654/43 Oct/Nov 2024

11 Fig. 11.1 shows the reactivity series of some metals. The element carbon is also included in the list. sodium most reactive magnesium aluminium carbon zinc iron copper least reactive Fig. 11.1 (a) (i) Iron is extracted from the ore hematite by heating with carbon. Use Fig. 11.1 to state and explain how magnesium is extracted from magnesium ore. … … … [2] (ii) Sodium is more reactive than magnesium. Explain why. … … [1] (b) Carbon is used to extract an element, X, from its oxide. The equation for the reaction is shown. XO2 + C X + CO2 The sum of the relative formula masses of the reactants (XO2 + C) is 163. Calculate the relative atomic mass of X. [Ar: C, 12; O, 16] relative atomic mass of X = … [2] (c) Iron is extracted from iron oxide by reacting the iron oxide with aluminium. The equation for the reaction is shown. 2Al + Fe2O3 2Fe + Al 2O3 A mixture contains 162 g of aluminium and 800 g of iron oxide. Show that aluminium is the limiting reactant. [Ar: Al, 27; Fe, 56; O, 16] aluminium is the limiting reactant because … … … [3] (d) Magnesium displaces copper from copper chloride solution. The ionic equation for the reaction is shown. Mg + Cu2+ Mg2+ + Cu Explain why the reaction between magnesium atoms and copper ions involves both oxidation and reduction. … … … [2] (e) Complete the following sentences about oxidising agents and reducing agents. An oxidising agent is a substance which … another substance during a redox reaction. A reducing agent is a substance which … another substance during a redox reaction. [1] [Total: 11]

11 marks

Mark scheme: 11(a)(i) electrolysis ; 2 carbon is less reactive than magnesium / ORA / carbon cannot displace the magnesium from the magnesium ore ; 11(a)(ii) (idea that sodium atoms) form positive (sodium) ions more easily (than magnesium) / 1 (idea that sodium atoms) lose electrons more easily (than magnesium) ; 11(b) Mr of CO2 = 44 / relative atomic mass of X = 163 – 44 / 163 – 32 – 12 ; 2 119 ; 11(c) (moles of Fe2O3 = 800 / 160 =) 5 ; 3 (moles of Al = 162 / 27 =) 6 ; (aluminium is limiting because) 6 mol is less than the (2  5 =) 10 mol (aluminium needed) or iron oxide is in excess because 5 mol is more than the (6 ÷ 2 =) 3 mol (iron oxide needed) ; 11(d) oxidation because magnesium atoms lose electrons ; 2 reduction because copper ions gain electrons ; 11(e) oxidises 1 and reduces ;

This question in 0654/43 Oct/Nov 2024

5 Fig. 5.1 shows the electronic configuration of an aluminium atom. Al Fig. 5.1 (a) Describe how Fig. 5.1 shows that aluminium is in period 3 of the Periodic Table. … [1] (b) An aluminium atom, Al, forms an aluminium ion, Al 3+. Describe, in terms of electrons, how an aluminium ion is formed. … … [2] (c) Aluminium reacts with chlorine to make aluminium chloride. Aluminium chloride is an ionic compound. (i) Complete the sentence about ionic bonds. An ionic bond is a … electrostatic attraction between … charged ions. [2] (ii) Tick (✓) the correct property of ionic compounds. generally insoluble in water good electrical conductivity when solid high melting point [1] (d) Aluminium and chlorine are elements. Aluminium chloride is a compound. Describe the difference between an element and a compound. element … … compound … … [2] 37 35 (e) Explain why 17Cl and 17Cl are isotopes of the element chlorine. … … … [2] [Total: 10]

10 marks

Mark scheme: 5(a) (aluminium has) 3 occupied electron shells ; 1 5(b) (aluminium atom) loses electrons ; 2 (aluminium atom) loses 3 electrons ; 5(c)(i) strong / owtte ; 2 oppositely / owtte ; 5(c)(ii) 1 Generally insoluble in water Good electrical conductivity when solid High melting point ✓ ; 5(d) element 2 contains only one type of atom / idea that all the atoms have the same number of protons or same atomic number ; compound substance made of two or more different elements (chemically joined) ; 5(e) same number of protons / same atomic number / both have 17 protons / both have an atomic number of 17 ; 2 different numbers of neutrons / 37Cl has 20 neutrons but 35Cl has 18 neutrons / different mass number / 37Cl has a mass number of 37 but 35Cl has a mass number of 35 ;

This question in 0654/42 Feb/March 2025

6 (a) A sodium atom is represented with numbers next to its chemical symbol, as shown in Fig. 6.1. 23 Na 11 Fig. 6.1 Complete Table 6.1 to show the structure of a sodium atom. Table 6.1 number of atomic mass number number protons neutrons electrons 23 11 … … … [2] (b) Fig. 6.2 shows an outline of the Periodic Table. The letter E shows the position of an element in the Periodic Table. The letter E is not the chemical symbol of the element. E Fig. 6.2 Predict the electronic configuration of element E. Tick (3) one box. 2.2 2.8.2 2.3 2.8.3 [1] (c) Carbon-12 and carbon-13 are two isotopes of the element carbon. These isotopes of carbon have the same chemical properties. Explain why. … … [1] (d) State the type of oxide formed when carbon, a non-metal, reacts with oxygen to produce carbon dioxide, CO2. … [1] (e) Carbon dioxide is a greenhouse gas and causes global warming. Complete the sentences to describe how carbon dioxide causes global warming. Use words from the list. Each word can be used once, more than once, or not at all. absorbed reflected refracted stored Energy from the Sun reaches the Earth’s surface. Some energy is … back into space. Most of the energy is … by the Earth’s surface, causing an increase in temperature. The warm Earth emits energy. Some of this emitted energy is then … by greenhouse gases. When this energy is re-emitted, it can be transferred back to the Earth’s surface. [3] (f) Some coal burns to make 11 000 g of carbon dioxide gas. Calculate the volume occupied by 11 000 g of carbon dioxide gas. The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). [Ar: C, 12; O, 16] volume of carbon dioxide gas = … dm3 [3] [Total: 11]

11 marks

Mark scheme: 6(a) 2 atomic mass number of number number protons neutrons electrons 11 ; 23 11 12 ; 11 6(b) 2.8.2 ✓ ; 1 6(c) (the isotopes have) the same number of electrons / 1 the same electronic configuration ; 6(d) acidic (oxide) ; 1 6(e) reflected ; 3 absorbed ; absorbed / stored ; 6(f) Mr of CO2 = 44 ; 3 moles of CO2 = 11000  44 = 250 ; volume of CO2 = 250  24 = 6000 dm³ ;

This question in 0654/41 May/June 2025

5 A student investigates black ink using paper chromatography. Fig. 5.1 shows: • the chromatogram the student obtains • the measurements the student may make. measurements solvent front spot Y spot X A B C D start line black ink Fig. 5.1 (a) State if black ink is a pure or impure substance. Use Fig. 5.1 to explain your answer. statement … explanation … … [1] (b) State which two measurements on Fig. 5.1 are needed to calculate the Rf value of spot X. … and … [1] (c) The student calculates the Rf value of spot Y to be 0.80. The distance travelled by spot Y is 2.8 cm. Calculate the distance travelled by the solvent. distance travelled by solvent = … cm [2] (d) Paper chromatography has a stationary phase and a mobile phase. The stationary phase is a solid. The mobile phase is a liquid. Describe what happens to the separation and motion of the particles when a solid changes to a liquid. separation … … motion … … [2] (e) Different substances have different structures. Draw one line from each statement to the structure. statement structure The substance is a gas. +– +– –++ –+ –+ +– – + – + – +– – +– +– + –+ ––+– +– The substance is an + – + + + – + ionic solid. – + – – + + – + + – – + – + – – ++ – + – – + + – + + The substance is a solid metal. The substance is a giant covalent solid. [4] [Total: 10]

10 marks

Mark scheme: 5(a) (impure because) 1 idea that there is more than one spot; 5(b) A and B; 1 5(c) Rf = distance travelled by substance / 2 distance travelled by solvent 0.80 = 2.8 ÷ distance travelled by solvent / distance travelled by the solvent = 2.8 ÷ 0.80; 3.5 (cm); 5(d) separation 2 idea that particles in a liquid are slightly further apart than in a solid (but still touching) / ORA; motion idea that particles in a liquid move faster (than in a solid) / ORA / idea that particles move randomly in a liquid but vibrate (about a fixed position in a solid); 5(e) 4 ;;;;

This question in 0654/43 May/June 2025

6 Fig. 6.1 shows the structure of magnesium oxide. Key O2– Mg2+ Fig. 6.1 (a) Deduce the formula of magnesium oxide. formula … [1] (b) Oxides can be classified as acidic, basic or amphoteric. Classify magnesium oxide. Explain your answer. classification … explanation … … [2] (c) Magnesium is in Group II and period 3 of the Periodic Table. Determine the electronic configuration of a magnesium atom. … [1] (d) Magnesium occurs naturally in three stable isotopes, 24Mg, 25Mg and 26Mg. Describe the similarity and the difference between the three isotopes. similarity … difference … [2] (e) The compound magnesium sulfate, MgSO4, is found in sea water. Calculate the amount (mol) of magnesium sulfate in a 3.05 g sample of magnesium sulfate where all the magnesium atoms are the isotope 26Mg. [Ar: O, 16; S, 32] amount (mol) of magnesium sulfate = … [3] (f) A student measures the boiling point of a sample of sea water. The boiling point is 102 °C. Describe how the student knows that the sea water is not pure water. … … [1] [Total: 10]

10 marks

Mark scheme: 6(a) MgO; 1 6(b) basic; 2 (because) magnesium is a metal; 6(c) 2.8.2; 1 6(d) similarity 2 same number / amount of protons / same atomic number / all have an atomic number of 12; difference different number / amount of neutrons / different mass number; 6(e) Mr of MgSO4 = 26 + 32 + (4  16) = 122; 3 mol = mass ÷ Mr / 3.05 ÷ 122; = 0.025; 6(f) idea that (pure) water has a boiling point of 100 °C; 1

This question in 0654/43 May/June 2025

6 (a) Table 6.1 shows some information about the particles in atoms. Complete Table 6.1. Table 6.1 particle relative charge relative mass electron 0.0005 … neutron 1 … proton +1 … [2] (b) An ion of sodium is shown. 2 3 1 1Na+ Complete the sentence about this sodium ion. This sodium ion contains 11 protons, … electrons and … neutrons. [2] (c) Fig. 6.1 shows four symbols. 3 2 3 3 3 5 3 7 1 7Cl 1 7Cl 1 8Cl 1 7Cl Fig. 6.1 State which symbol is not an isotope of chlorine. … [1] (d) Chlorine, Cl 2, is a simple molecule. Draw a dot-and-cross diagram to show the bonding in chlorine. You only need to show the outer-shell electrons. [2] (e) Fig. 6.2 shows a chlorine molecule and a sodium chloride lattice. sodium ion + – + – + – Cl + – + chloride ion – + – + – + – Cl + – + – + – + Fig. 6.2 Explain why chlorine is a gas at room temperature but sodium chloride is a solid at room temperature. Use ideas about: • the bonding in sodium chloride and in chlorine • forces. … … … … … … [3] [Total: 10]

10 marks

Mark scheme: 6(a) 2 particle relative charge relative mass electron –1 0.0005 neutron 0 1 proton +1 1 3 correct for 2 marks 1 or 2 correct for 1 mark 6(b) 10 electrons ; 2 12 neutrons ; 6(c) 35Cl ; 1 18 6(d) 2 1 mark shared pair of electrons between chlorine atoms 1 mark for rest of structure correct 6(e) chlorine is covalent and sodium chloride is ionic ; 3 chlorine has weak intermolecular forces ; sodium chloride has strong electrostatic forces / sodium chloride has strong forces between oppositely charged ions ;

This question in 0654/43 Oct/Nov 2025