Isotopes — Paper 4 · IGCSE Sciences - Co-ordinated (Double) 0654

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

8 (a) (i) Using information in the Periodic Table on page 32, calculate the relative molecular masses of the gases nitrogen and chlorine. Mr (nitrogen) = … Mr (chlorine) = … [1] (ii) Using your answer to (a)(i), state and explain which of these two gases diffuses at the greater rate. gas … explanation … … [1] (b) Chlorine occurs naturally as a mixture of mainly two isotopes, chlorine-35 and chlorine-37. Complete Table 8.1 to show some information about the atomic structures of these isotopes. Table 8.1 isotope number of nucleons number of protons number of neutrons number of electrons chlorine-35 35 17 chlorine-37 37 17 [2] (c) A student mixes colourless aqueous solutions of chlorine and sodium bromide. Fig. 8.1 shows the apparatus she uses. chlorine solution mixture sodium bromide solution Fig. 8.1 (i) A reaction occurs when chlorine solution is mixed with sodium bromide solution. Predict and explain the student’s observation when these solutions are mixed. observation … explanation … … [2] (ii) Write a word equation for the reaction that occurs when these solutions are mixed. … [2] (d) The student adds an orange solution of bromine to a colourless solution of sodium fluoride. Predict and explain the student’s observation when the solution of bromine is added to the solution of sodium fluoride. observation … explanation … … [2] [Total: 10]

10 marks

Mark scheme: 8(a)(i) Mr (nitrogen) = 28 Mr (chlorine) = 71 ; 1 8(a)(ii) nitrogen rate of diffusion increases with decreasing molecular mass / lighter particles move faster than heavier particles (with same energy / in gas at same temperature) ; 1 8(b) correct neutron column ; correct electron column ; isotope number of neutrons number of electrons chlorine-35 18 17 chlorine-37 20 17 2 8(c)(i) yellow / orange solution ; chlorine displaces bromine / chlorine is more reactive than bromine / bromine is formed ; 2 8(c)(ii) chlorine + sodium bromide Æ bromine + sodium chloride bromine as product ; all else correct ; 2 8(d) no change in colour / paler (due to dilution) ; no reaction because bromine is less reactive than fluorine / reference to trend in reactivity down Group VII ; 2

This question in 0654/41 May/June 2019

6 (a) An iron magnet picks up two iron nails as shown in Fig. 6.1. S N Fig. 6.1 Explain why the nails do not hang vertically. … … … [2] 60 (b) An isotope of iron has a nuclide notation 26Fe and decays by beta particle emission to an isotope of cobalt. (i) State what is meant by the term isotope. … … [1] (ii) Use nuclide notation to complete the symbol equation for this β-decay process. [2] 6026Fe … + … (c) An iron wire of length 0.50 m has a cross sectional area of 4.0 × 10–5 m2 and a resistance of 1.21 × 10–3 Ω. Calculate the resistance of an iron wire of length 0.25 m that has a cross sectional area of 8.0 × 10–5 m2. resistance = … Ω [3] (d) A block of iron is on a bench. The surface of the block of iron in contact with the bench has an area of 144 cm2. The mass of the block of iron is 13.6 kg. Calculate the pressure exerted by the block of iron on the bench in N / cm2. gravitational field strength = 10 N / kg pressure = … N / cm2 [3] [Total: 11]

11 marks

Mark scheme: 6(a) ref. to induced magnetism (in) nails ; two nail heads / north poles / like poles, will repel each other ; 2 6(b)(i) atoms having same atomic number / proton number and different mass number / neutron number ; 1 6(b)(ii) 60Co ; 27 0 e ; –1 2 6(c) evidence that resistance is halved by cross sectional area change ; evidence that resistance is halved by length change ; new resistance = 3.0 × 10–4 Ω ; 3 6(d) 136 N ; pressure = force / area OR 136 / 144 ; 0.94 (N / cm2) ; 3

This question in 0654/41 Oct/Nov 2019

11 Fig. 11.1 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. 11.1 (a) Fig. 11.2 shows the apparatus a teacher uses to place a piece of potassium into a bowl of water. potassium water Fig. 11.2 (i) The teacher places the piece of potassium into the water. Describe her observations. … … … [2] (ii) Predict how the observations would differ if she uses rubidium instead of potassium. Explain your answer. … … … [2] (b) Two isotopes of potassium are potassium-39 and potassium-41. Table 11.1 isotope number of protons number of neutrons number of electrons potassium-39 potassium-41 (i) Complete Table 11.1. [3] (ii) Predict if there are any differences in the reactions of these isotopes with water. Explain your answer. prediction … explanation … … [2] [Total: 9]

9 marks

Mark scheme: 11(a)(i) melts ; bubbles ; flame ; moves across surface / floats ; max 2 2 11(a)(ii) more vigorous / owtte ; reactivity increases down the group ; 2 11(b)(i) protons ; neutrons ; electrons ; isotope number of protons number of neutrons number of electrons potassium-39 19 20 19 potassium-41 19 22 19 3 11(b)(ii) no difference ; because of same number of electrons ; 2

This question in 0654/42 Oct/Nov 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

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

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

3 Carbon-14 is an unstable isotope which decays to produce nitrogen -14. (a) State what is meant by an isotope. … … [1] (b) Use the correct nuclide notation to complete the symbol equation for this decay process. 14 __ __ __ 6C __ N + __ [2] (c) Fig. 3.1 shows the percentage of carbon-14 in a sample. 100 90 80 % carbon-14 atoms remaining 70 60 50 40 30 20 10 0 0 10 000 20 000 30 000 40 000 50 000 age of sample / years Fig. 3.1 Use Fig. 3.1 to determine the half-life of carbon-14. half-life = … years [2] (d) The decay of unstable isotopes can also release gamma rays which are part of the electromagnetic spectrum. (i) On Fig. 3.2 write gamma in the correct position. visible infrared microwaves Fig. 3.2 [1] (ii) State the speed of the gamma rays produced by radioactive decay. … [1] (iii) A gamma ray has a wavelength of 2.0 × 10–11 m. Use your answer to (d)(ii) to calculate the frequency of this gamma ray. State the unit for your answer. frequency = … unit … [3] (iv) Draw lines to match each form of electromagnetic radiation to its use. form of electromagnetic uses radiation infrared medicine and security microwaves radio and TV communications radiowaves remote controls and intruder alarms X-rays satellite television and telephones [2] (e) All electromagnetic waves are transverse waves. Sound is an example of a longitudinal wave. Give one difference between transverse and longitudinal waves. … … [1] [Total: 13]

13 marks

Mark scheme: 3(a) same proton number and different neutron number ; 1 3(b) 14 7N ; 0 1β − ; 2 3(c) use of graph ; 6000 years ; 2 3(d)(i) gamma in left box ; 1 3(d)(ii) 3 × 108 m / s ; 1 3(d)(iii) (f=) v / λ or 3x108 / 2.0x10-11 ; 1.5 x 1019 ; Hz ; 3 3(d)(iv) ;; 2 3(e) transverse vibrations are perpendicular to energy transfer / longitudinal vibrations are parallel to energy transfer ; 1

This question in 0654/43 Oct/Nov 2021

2 Potassium is in Group I of the Periodic Table. (a) Potassium-39 is an isotope of potassium. (i) Explain what is meant by an isotope. … … … [2] (ii) Potassium-39 has a proton number (atomic number) of 19 and a nucleon number (mass number) of 39. Complete Table 2.1 to give the number of particles in: • a potassium atom • a potassium ion. Table 2.1 potassium atom, K potassium ion, K+ number of protons number of electrons number of neutrons [3] (b) Sodium is another element in Group I. Sodium reacts with water. Sodium hydroxide, NaOH, and hydrogen are made. Construct the balanced symbol equation for this reaction. … [2] (c) Fig. 2.1 is a dot-and-cross diagram which shows the electronic structure of a sodium atom and a fluorine atom. sodium atom fluorine atom Fig. 2.1 A sodium ion and a fluoride ion are formed when sodium reacts with fluorine. Complete the dot-and-cross diagram in Fig. 2.2 to show the electronic structure of a sodium ion and a fluoride ion. Include the charges on the ions. sodium ion fluoride ion Fig. 2.2 [2] (d) A student wants to identify a metal halide, compound X. (i) The student does a flame test, as shown in Fig. 2.3. flame test wire flame flame test wire test wire bunsen burner hydrochloric compound X acid Fig. 2.3 The flame colour turns from blue to yellow. State the name of the metal ion in compound X. metal ion … [1] (ii) The student dissolves compound X in distilled water. The student then adds a little dilute nitric acid followed by a few drops of aqueous silver nitrate. A white precipitate is formed. Suggest which halide ion is in compound X. Choose from the list. bromide chloride iodide halide ion … [1] [Total: 11]

11 marks

Mark scheme: 2(a)(i) atoms with the same, proton or atomic number / number of protons ; (but) different, nucleon / mass number / number of neutrons ; 2 2(a)(ii) potassium atom, K potassium ion, K+ number of protons 19 19 number of electrons 19 18 number of neutrons 20 20 ;;; 3 2(b) 2Na + 2H2O → 2NaOH + H2 ;; 2 Question Answer Marks 2(c) ;; 2 2(d)(i) sodium ; 1 2(d)(ii) chloride ; 1

This question in 0654/42 Feb/March 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

11 (a) Element X is found in Group II of the Periodic Table. State the formula of the ion formed by element X. Tick (3) one box. X2– X6– X2+ X6+ [1] (b) Determine the formula of the compound formed by NH4+ and CO32– ions. formula = … [1] (c) The number of subatomic particles in an ion is different from the number in a neutral atom. Table 11.1 shows information about two different ions. Complete Table 11.1. Table 11.1 proton (atomic) nucleon (mass) ion protons neutrons electrons number number Al 3+ 13 27 13 10 … F– 9 19 9 10 … [2] (d) Carbon has the electronic structure 2.4. Oxygen has the electronic structure 2.6. Carbon reacts with oxygen to make carbon dioxide, CO2. Complete the dot‑and‑cross diagram in Fig. 11.1 to show the bonding in carbon dioxide. Only show the outer‑shell electrons. O C O Fig. 11.1 [2] (e) Carbon exists in several different forms. Graphite and diamond are two of these forms. Fig. 11.2 shows the structures of graphite and diamond. graphite diamond Fig. 11.2 (i) Explain why the structure of graphite makes it suitable for use as a lubricant. … … … [2] (ii) Explain why the structure of diamond makes it suitable for use in cutting tools. … … … [2] [Total: 10]

10 marks

Mark scheme: 11(a) X2+ ; 1 11(b) (NH4)2CO3 ; 1 11(c) ion proton (atomic) number nucleon (mass) number protons neutrons electrons Al 3+ 13 27 13 14 10 F- 9 19 9 10 10 ;; 2 Question Answer Marks 11(d) double bonds between C and O atoms ; rest of structure correct ; 2 11(e)(i) (graphite has) weak forces between the layers ; layers can slide over each other / owtte ; 2 11(e)(ii) any two from: (diamond) has many strong bonds ; bonds are covalent bonds ; (diamond has) giant molecular / macromolecular / giant tetrahedral / lattice / giant covalent, structure ; 2

This question in 0654/43 May/June 2023

2 The element carbon exists as 3 naturally occurring isotopes. Fig. 2.1 shows an atom of one isotope, carbon-14. – – … … + + + + + + – – … – – Fig. 2.1 (a) (i) Complete the labels on Fig. 2.1. [3] (ii) Fig. 2.2 shows an atom of a different isotope of carbon. – – – – – – Fig. 2.2 Complete Fig. 2.2 to show the particles in the nucleus of one of the other two isotopes of carbon. [2] (iii) The different isotopes of carbon all have the same chemical properties. Explain why. … … [1] (b) Carbon reacts with oxygen to form carbon dioxide. State the test for carbon dioxide and its positive result. test … positive result … [2] (c) Compounds that only contain carbon and hydrogen can form compounds with only single covalent bonds. Complete the sentence about these compounds. Choose words from the list. addition alkenes hydrocarbons polymers saturated unsaturated Carbon and hydrogen compounds with only single covalent bonds are called … … . [2] [Total: 10]

10 marks

Mark scheme: 2(a)(i) 3 proton ; electron ; neutron ; 2(a)(ii) 6 protons ; 2 6 or 7 neutrons ; 2(a)(iii) same number of electrons in the outer shell ; 1 2(b) test: limewater ; 2 observation: milky / cloudy / white precipitate ; 2(c) saturated ; 2 hydrocarbons ;

This question in 0654/42 Oct/Nov 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

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

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

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