1 6 a i Ionic Bonding 1

Ionic Bonding Exam Questions

Q1.The bonding in magnesium oxide, MgO, is

A ionic.

B metallic and ionic.

C ionic and covalent.

D metallic and covalent.

(Total for question = 1 mark)

Q2.Which of these equations represents the electron affinity of chlorine?

A Cl2(g) + 2e- → 2Cl-(g)

B Cl2(g) - 2e- → 2Cl-(g)

C ½Cl2(g) + e- → Cl-(g)

D Cl(g) + e- → Cl-(g)


Q3.Which of these electron density maps best represents the bonding in the compound lithium iodide, LiI?


Q4.Which of the following does not have exactly 10 electrons?

A An ion of fluorine, F−

B A molecule of methane, CH4

C A molecule of nitrogen, N2

D An ion of sodium, Na+


1.6 Bonding SpecificationStudents will be assessed on their ability to:

Ionic bonding

a. recall and interpret evidence for the existence of ions, limited to physical properties of ionic compounds, electron density maps and the migration of ions, eg electrolysis of aqueous copper chromate(VI)

b. describe the formation of ions in terms of electron loss or gain

c. draw electron configuratio

Q5.A drop of concentrated nickel(II) sulfate solution, which is green, is placed on moist filter paper on a microscope slide and the ends of the slide are connected to a 24 V DC power supply. After ten minutes,

A a blue colour has moved towards the negative terminal and a yellow colour towards the positive terminal.

B a blue colour has moved towards the positive terminal and a yellow colour towards the negative terminal.

C a green colour has moved towards the negative terminal but there is no other visible change.

D a green colour has moved towards the positive terminal but there is no other visible change.


Q6.Which of the following represents the process occurring when the enthalpy change of atomization of bromine is measured?

A ½Br2(l) → Br(g)

B ½Br2(g) → Br(g)

C Br2(l) → Br+(g) + Br−(g)

D Br2(g) → Br+(g) + Br−(g)


Q7.Which of the following statements is evidence for the existence of ions in ionic compounds?

A Ionic compounds, in the solid state, conduct electricity. B When any ionic compound in solution is electrolysed, the migration of ions

can be seen. C In electron density maps for ionic compounds, there is no single line

representing electron density that surrounds both cations and anions. D In electron density maps for ionic compounds, there are some single lines

representing electron density that surround both cations and anions.(Total for question = 1 mark)

Q8.Going down Group 1 from lithium to rubidium

A the radius of the atom decreases.

B the radius of the ion decreases.

C the first ionization energy decreases.

D the polarizing power of the ion increases.


Q9.Magnesium chloride, MgCl2, has two lattice energy values quoted in the data booklet. The first is the experimental value, obtained from the Born-Haber cycle, −2526 kJ mol−1; the second is the


Ionic bonding




theoretical value, −2326 kJ mol−1. Why are the two values different?

A The cation polarizes the anion leading to some covalent bonding.

B The anion polarizes the cation leading to some covalent bonding.

C Magnesium chloride is a covalent substance.

D The results from the Born-Haber cycle are too inaccurate to be reliable.


Q10.The first ionization energies, in kJ mol-1, of four elements with consecutive atomic numbers are shown below.

A 1680B 2080C 496D 738

(a) Which element could be an inert gas?(1)

A B C D

(b) Which element could be X in a covalent compound with formula HX?(1)

A B C D

(c) Which element could be Y in an ionic compound with formula YH2?(1)

A B C D

(Total for question = 3 marks)

Q11.Which equation represents the reaction for which the enthalpy change is the lattice energy of sodium fluoride, NaF?

A Na(s) + ½F2(g) → NaF(s) B Na(g) + F(g) → NaF(s) C Na+(g) + F−(g) → NaF(s) D Na(g) + ½F2(g) → NaF(s)


Q12.Which of these statements is incorrect?

A The atomic radius of metals increases down a Group.

B The trend in the melting temperature of successive elements across Period 2 is similar to that in Period 3.

C A metallic structure is held together by attractions between metal atoms and delocalized electrons.

D Na+ and O2- ions are isoelectronic.


Ionic bonding





Q13.Which of the following graphs shows the variation in the ionic radius of the Group 2 elements?


Q14.The ionic radii in nm of some ions are given below.

(a) Which of the following compounds has the most exothermic lattice energy? They all have the same crystal structure.

(1)

A LiF B LiCl C CaO D CaS

(b) Which of the following compounds will show the greatest difference between the experimental (Born-Haber) lattice energy and that calculated from a purely ionic model?

(1)

A LiF B Li2O C CaO D CaS

Total for question = 2 marks)

Q15.Element R is in Group 1 of the Periodic Table and element T is in Group 6. R and T are not the symbols for the elements.(a) The compound of R and T will have the formula

(1)

A RT B RT6 C RT2 D R6T

(b) The compound of R and T will have bonding which is predominantly(1)

A ionic. B covalent. C dative covalent. D metallic.


Ionic bonding




(c) In terms of its electrical conductivity, the compound of R and T will(1)

A conduct when solid and liquid.

B conduct when solid but not when liquid.

C conduct when liquid but not when solid.

D not conduct when solid or liquid.


Q16.Going across the Periodic Table from sodium to aluminium,

A the melting temperature increases.

B the radius of the atom increases.

C the radius of the metal ion increases.

D the bonding in the element changes from metallic to covalent.


Q17.Which of these ions has the greatest ability to polarize an anion?

A Ba2+ B Ca2+ C Cs+ D K+


Q18.Which of the following has the smallest ionic radius?

A F− B Na+ C Mg2+ D O2−


Q19.The graph below represents the successive ionization energies of an element X plotted against the number of the electron removed. X is not the symbol for the element.

(a) From this graph it is possible to deduce the group in the Periodic Table to which X belongs. X is in

(1)

A Group 1 B Group 3 C Group 5 D Group 7

(b) From the graph it is possible to deduce that the most stable ion of X will be(1)

A X3+ B X+ C X− D X3−


Q20.Theoretical lattice energies can be calculated from electrostatic theory. Which of the following affects the magnitude of the theoretical lattice energy of an alkali metal halide, M+X− ?

A The first electron affinity of X. B The first ionization energy of M. C The enthalpy of atomization of M. D The radius of the X− ion.


Q21.Which of the graphs shows (from left to right) the trend in the ionic radius of the isoelectronic ions N3−, O2−, F−, Na+, Mg2+, Al3+?


Q22.The Born-Haber cycle for the formation of sodium chloride from sodium and chlorine may be represented by a series of steps labelled A to F as shown.

(a) (i) Complete the table below by adding the letters A to F next to the corresponding energy changes.

(3)

(ii) Calculate the first electron affinity of chlorine, in kJ mol−1, from the data given.(2)

(b) Lattice energies can be calculated from electrostatic theory (theoretical values) as well as by Born-Haber cycles (experimental values).

(i) Comment on the fact that there is close agreement between the values for sodium chloride, NaCl.

(1)*(ii) Explain, in terms of chemical bonding, why the experimental value for silver iodide, AgI, is more exothermic than the value calculated theoretically for the same compound.

(2)

*(c) Suggest why the first ionization energies of the Group 1 elements decrease down the group.

(2)


Q23.(a) Briefly describe an experiment, with a diagram of the apparatus you would use which shows that there are oppositely charged ions in copper(II) chromate(VI), CuCrO4. Describe what you would expect to see.

4

Diagram

(b) The ions in an ionic lattice are held together by an overall force of attraction.

(i) Describe the forces of attraction in an ionic lattice.

(1)

(ii) Suggest two forces of repulsion which exist in an ionic lattice.

(2) .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

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(c) Part of the Born-Haber cycle for magnesium oxide, MgO, is shown below.

(i) Complete the empty box with the appropriate formulae and state symbols.

(2)

(ii) Identify the enthalpy changes represented by the letters A and C.

(2) ..............................................................................................................................................

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(iii) Give the expression for the enthalpy change F in terms of the other enthalpy changes to A and E.

(1)

F =

(d) The lattice composed of the ions Mg2+ and O2− is stronger than a lattice composed of the ions Mg+ and O− .

(i) Explain, in terms of the charges on the ions and the size of the cations, why this is so.

(2) ..............................................................................................................................................

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(ii) Suggest how the lattice energy of Mg2+O2− would differ from that of Mg+O−.

(1) ..............................................................................................................................................

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Q24.This question is about the properties of ions and ionic compounds.(a) Solid calcium carbonate, CaCO3, has a giant ionic structure.

(i) Draw a diagram (using dots or crosses) for a calcium ion. Show ALL the electrons and the charge on the ion.

(2)

(ii) Complete the electronic configuration for a calcium ion.(1)

1s2..............................................................................................................................................

(iii) Would you expect a calcium ion to be bigger, smaller or the same size as a calcium atom? Give TWO reasons to explain your answer.

(2) ..............................................................................................................................................

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..............................................................................................................................................(iv) Explain why ionic compounds have relatively high melting temperatures.

(2) ..............................................................................................................................................

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(b) Changes in the concentration of ions in a solution can be estimated by measuring the electrical conductivity of the solution.

(i) Explain why solutions of ions are able to conduct electricity.(1)

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..............................................................................................................................................(ii) Suggest why aqueous solutions of calcium chloride, CaCl2(aq), and barium chloride, BaCl2(aq), of the same molar concentration, have different electrical conductivities.

(1) ..............................................................................................................................................

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(iii) 1 kg of a solution contains 0.100 mol of calcium ions, Ca2+.

What is the concentration of the calcium ions by mass in parts per million (ppm)?

[Assume the relative atomic mass of calcium is 40.](2)

.....................................ppm*(c) Some buildings are made from limestone, which is mainly calcium carbonate. Gases in the atmosphere such as sulfur dioxide, SO2, and nitrogen dioxide, NO2, can be responsible for damaging these buildings.

Describe how these gases come to be present in the atmosphere and explain how they can damage a limestone building.

(3) ..............................................................................................................................................

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(d) The lattice energy of calcium chloride, CaCl2, is -2258 kJ mol-1 based on an experimental Born-Haber cycle and -2223 kJ mol-1 based on theoretical calculations.

Would you expect its bonding to match the ionic model? Justify your answer.

(1) ..............................................................................................................................................

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..............................................................................................................................................(Total for question = 15 marks)

Q25.This question is about lithium iodide, an ionic salt.(a) Draw dot and cross diagrams for the lithium and iodide ions. Show all the electrons in the lithium ion but only outer shell electrons in the iodide ion.

(2)

(b) On the Born-Haber cycle below, fill in the missing formulae (including state symbols) and the missing enthalpy change.

(3)

(c) Calculate the electron affinity of iodine, Eaff1[I(g)], using the data below.

(2)

(d) The experimental lattice energy for lithium iodide is −759 kJ mol−1. The theoretical lattice energy is different from this value.

Will the experimental lattice energy be more negative or less negative than the theoretical lattice energy? Justify your answer.

(3) ..............................................................................................................................................

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(e) State and explain how electron affinity values change as you go down Group 7 from chlorine to iodine.

(2) ..............................................................................................................................................

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Q26.(a) (i) Complete the electronic configuration of the magnesium atom.

(1)1s2.....................................................................................................................................................

(ii) Complete the electronic configuration of the chlorine atom.(1)

1s2.....................................................................................................................................................

.(b) (i) Write the equation, including state symbols, for the reaction of magnesium with chlorine.

(2)

(ii) Name the type of bonding present in magnesium chloride.(1)

..............................................................................................................................................(iii) Draw a diagram (using dots or crosses) to show the bonding in magnesium

chloride. Include ALL the electrons in each species and the charge present.(3)

(c) State the type of bonding that exists in solid magnesium.(1)

Type ...............................................................................................................................................

*(d) Explain fully why the melting temperature of magnesium is higher than that of sodium.

(3)..........................................................................................................................................................

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Q1.No Examiner's Report available for this question


















Q22.In (a)(i), it was pleasing to see the energy changes on the Born-Haber cycle identifi ed correctly. Part (a)(ii) proved to be more demanding, with many candidates being unable to derive a correct expression for the fi rst electron affi nity of chlorine. Frequently, a candidate's working led to an answer of +360 kJ mol-1, which was then amended to a fi nal answer of -360 kJ mol-1 without any comment.

The best answers started with an expression of the form "D = ......", with subsequent rearrangement of the expression to find the unknown, F, as shown below:-

In the second example above, one out of the two available marks has not been awarded due to a transposition error. These occurred quite frequently. Consequential marking allowed the award of one mark for the subsequent value of the fi rst electron affi nity for chlorine.

In (b)(i), answers often contained a comment on the mathematical difference between the experimental and theoretical lattice energies rather than to the fact that the values were in close agreement and, therefore, that the bonding in sodium chloride is almost completely ionic. Part (b)(ii) revealed

that some candidates did not understand the link between there being a signifi cant difference in the lattice energies and the nature of the bonding in a compound.

Part (c) was extremely well-answered, with all the relevant factors being included, as illustrated in the response below:-

Q23.(a)The majority of candidates described a method involving electrolysis.

Results Plus: Examiner CommentsThis response scored three marks out of four. Both a negative and a positive electrode are shown (although the fact that the longer terminal was shown incorrectly as being negative and the shorter terminal was shown incorrectly as being positive was not penalised). The yellow colour has been shown to migrate towards the positive electrode and the blue colour is shown migrating towards the negative electrode. The only omission is that the movement of ions has not been specifically mentioned in the answer.

Results Plus: Examiner TipAlways draw diagrams that are fully labelled, thereby relaying the maximum amount of information.

(b)Part (b)(i) was very well-answered. The most common error was to omit the word "ions". Very few scored both the marks in (b)(ii). The repulsion between like-charged ions was

acknowledged, but the repulsion between electron clouds around the ions (regardless of their charge) was frequently overlooked.

Results Plus: Examiner CommentsPart (b)(i) scores the mark as both positive and negative ions are included in the response. Part (b)(ii) scores both marks: the first mark for mention of ions of the same charge repelling and the second mark for acknowledging that electron clouds repel.

Results Plus: Examiner TipConsider the forces of attraction and of repulsion in an ionic lattice.

Results Plus: Examiner CommentsPart (b)(i) scores the mark for mention of both positive and negative ions. Part (b)(ii) did not score. One mark is negated by the mention of "magnetic" repulsion between ions of the same charge. The second scoring point in (b)(ii) is not addressed in this response.

(c)The majority of answers to (c)(i) were correct. In (c)(ii), however, although the enthalpy

change of formation was well-known, the next answer often simply referred to "ionization energy" or just "second ionization energy" instead of the sum of the first plus second ionization energies (of magnesium). If the answer to (c)(iii) was incorrect, then normally the signs were all the wrong way round.

Results Plus: Examiner CommentsThis is a correct response, clearly laid out.

Results Plus: Examiner CommentsIn (c)(i), both the two species and the two state symbols are correct. In (c)(ii), 'formation' scores a mark, but 'second ionization energy' is incorrect. The answer should have stated that this enthalpy change is the sum of the first two ionization energies. Part (c)(iii) is correct.

Results Plus: Examiner TipPractise questions such as (c)(iii) so that you can work your way round a Born-Haber cycle.

(d) (i)Unfortunately, many candidates did not read the question carefully and mention the effect on the ionic bonding of changing the charge on both the cation and anion. The fact that the Mg2+ cation is smaller than a Mg+ cation was appreciated by the majority of candidates.

Results Plus: Examiner CommentsThis answer scored both marks. Any comparison between the size of the O− and the O2−

ions was ignored, as the question only required a comparison between the size of the Mg2+ and the Mg+ cations.

Results Plus: Examiner TipAlways read the question carefully so as to ascertain exactly what you are required to consider in your answer.

(d) (ii)This was generally well-answered, except when candidates did not realise that this was requiring a comparison of the magnitude of the lattice energies rather than just stating that "the Mg2+O2- lattice is stronger".

Q24.(a) (i-ii)

Although for many this question was an easy start to the structured questions, a significant minority dropped at least one mark.

Surprisingly, this occurred in part (i) as well as part (ii), with an incorrect number of electron shells being the most common way to fail to score.

It's worth reminding candidates that transfer of key skills from GCSE, such as 'dot and cross' diagrams, is a feature of AS and they should not just focus their revision on new concepts, such as s, p and d orbitals.

Results Plus: Examiner CommentsThis is a clear, well presented answer to part (i), scoring both marks. However, it looks like the candidate has attempted (incorrectly) to give the electronic configuration for a calcium atom in part (ii).

Results Plus: Examiner TipPay careful attention to anything written in bold on the paper. It's done deliberately to help guide you towards answering the question. In this case it shows the question requires the electron configuration of the ion, not the atom.

(a) (iii-iv)

It was quite rare to award two marks in part (iii) and this item did help discriminate at the higher grades.

Whilst the vast majority recognised the ion was smaller, justifi cations were not always clear. For instance, many described simply loss of electrons, rather than loss of an electron shell, which

was not quite creditworthy. In addition, the idea of increasing effective nuclear charge, whilst acceptable in this context, did lead to a number of responses that suggested some candidates believed the actual nuclear charge was increasing, rather than the increase of its net effect on the remaining electrons. The best answers using this approach made it clear the number of protons remained the same, but now outweighed the number of electrons.

Part (iv) showed that most candidates understood the clear link between the strength of the many ionic bonds in a lattice and related this clearly to the input of energy needed to break up the structure. A few failed to score in this question either because they answered in terms of intermolecular forces or metallic bonds.

Results Plus: Examiner CommentsIn part (iii) 'stronger positive charge' without further clarification seems to imply more protons in the nucleus, so this answer was only awarded one mark, for loss of an electron shell.

Results Plus: Examiner TipThis answer would have been improved if the candidate had clarified why they believed they were subject to 'greater positive charge' for example by stating that the ion has more protons than electrons.

(b) (i)

The majority of candidates believed that delocalised electrons caused conductivity in ionic solutions. Of those who recognised the charged particles were ions, most went on to score the mark by emphasizing their freedom to move.

Results Plus: Examiner CommentsThis answer didn't score as, although it recognises the movement of charged particles is needed for a substance to conduct, it states, incorrectly, that in the case of a solution those particles are electrons.

(b) (ii)

The misconception regarding electrons in b (i) further hindered candidates in this item. A very simple answer regarding the size of the ions affecting the conductivity would have sufficed. It was acceptable for such an argument to be based on the ions alone, or in their hydrated form, that they were different sizes, without any further justification.

However, many candidates tried to justify the difference in terms of number of electrons, as they seemed to believe, as shown in part (i), that compounds release electrons on dissolving to allow conduction.

(b) (iii)

This calculation seemed unfamiliar to some candidates who, despite often scoring marks on calculations in questions 16 and 17, found this very difficult.

Although essentially a scaling exercise, many did not appreciate this and left their answer as parts per thousand. Many others divided through by a million rather than scaling up to parts per million. As this is a relatively straightforward task, the poor responses from some centres suggests its relative novelty to the specification means it isn't as well practised as some other numerical tasks.

Results Plus: Examiner CommentsAlthough this candidate is unsure how to scale to parts per million, they have made some effort to show what calculations they are attempting and label their answers accordingly. Hence we were able to award this candidate 1 mark for correctly determining the mass of calcium present in the solution.

Results Plus: Examiner TipTry to always label any values you have calculated so it is clear to the examiner what you are attempting to do.

(c)

Many responses showed a good understanding of the processes involved in this question and examiners were pleased to see generally sound chemical principles used to explain a 'real life' problem. When candidates failed to score it was generally due to omissions rather than incorrect chemistry. For instance, some ignored the first part of the question and didn't discuss the source of the gases. Others gave vague generic answers for the source, such as 'pollution from factories or industry'.

However, some excellent explanations of the formation of nitrogen oxides in car engines were seen from more able candidates. Some responses for the third mark did not score as they assumed the process was just physical, rather than chemical, tending to just describe erosion and not any preceding chemical reaction.

Results Plus: Examiner CommentsThis answer shows understanding that a chemical reaction with the limestone is integral to the process damaging the building, but has not recognised the acidic nature of the two gases in aqueous solution. To improve, the candidate should have followed the guidance in the question and considered how the gases came to be present in the atmosphere in the first place.

(d)

It was not expected that candidates should recall whether the bonding in calcium chloride is considered almost completely ionic or partly covalent, but that they should use the data to help form an opinion. Just under half the candidates managed to do this, with many of those arguing that the difference was small enough that the substance could be considered to match the ionic model. A minority of candidates came close to scoring by attempting to justify covalent character in terms of polarization, but neglected to use the data to support their argument.

Results Plus: Examiner CommentsThis candidate makes a statement that could be correct, as the specification does not expect candidates to recall the precise level of difference in theoretical and experimental lattice energies. However, they did not use the data to support their answer so just missed out on the mark.

Results Plus: Examiner TipData and information in the stem of a question is there to help candidates. Always read it carefully to see if it could be useful in your written answer.

Q25.(a)Failure to read the question often cost a mark when iodine inner electrons were omitted.

Many candidates also omitted charges on the ions which should always be included.

Results Plus: Examiner CommentsAt first sight this a perfect answer. The candidate has shown how the ions are formed from the atoms concerned.Unfortunately, the candidate has failed to read the question fully 'show all the electrons in the lithium'.

Results Plus: Examiner TipCheck you have answered the question asked.

Results Plus: Examiner CommentsThe electron configurations are fine but there are no charges on the ions.

Results Plus: Examiner TipRemember to include charges on ions in dot and cross diagrams.

(b) - (c)The first part was very discriminating with an equal proportion of candidates gaining each mark from zero to four.

States or charges were often missing from the gaseous ions.

While the element lithium was usually correct, iodine seemed unfamiliar. Many thought iodine was a gas or liquid, and most thought it was monatomic. The symbol for atomisation including square brackets and the symbol for the starting material were rarely correct.

In contrast with part (b) this was generally quite well done with about half the candidates gaining full credit, for the correct answer with the correct sign. This was pleasing as the calculation may not have been as simple as the standard calculation of lattice energy.

Common errors were failure to give the sign, doing the wrong subtraction to obtain a positive sign or entering the incorrect data.

Results Plus: Examiner CommentsThe state symbols are missing from the gaseous ions.The candidate does not understand that enthalpy change of atomisation refers to one mole of atoms and they think the symbol includes the product rather than the starting material for atomisation. Though they know that iodine is diatomic and that half a mole is needed, they do not know that iodine is a solid.The reasoning of the calculation is clear and gives the correct answer.

Results Plus: Examiner TipBe careful to learn the complete symbols for the enthalpies and energies involved in lattice energy calculations.

Results Plus: Examiner CommentsThe gaseous ions and lithium solid are fine.They have the wrong state for iodine but the correct amount of the diatomic molecule.They have used the product symbol without a state for the atomisation enthalpy.They have made an arithmetic error with the last sign in the calculation, but they still get a mark for clear and correct working.

Results Plus: Examiner TipShow all working clearly in calculations.

(d)The first mark was achieved by less than half the entry, as some still insisted on terms like increase or decrease. Various justifications were acceptable, whatever the first statement. The most common correct justification was for a degree of covalency. Care was needed to refer to distortion or polarization of iodide ions, the terms iodine 'atoms' or even 'molecules' were regrettably frequent.

Results Plus: Examiner CommentsThe answer identifies there is some covalent character in the bonding, and explains this arises due to the polarization of the anion by the cation.Unfortunately the reference to energy is incorrect.Notice that 2 marks are scored in spite of this error.

Results Plus: Examiner TipYour reasoning often gains more credit than the main answer to a question as it does here.

Results Plus: Examiner CommentsThis is an example of a perfect answer. Notice also that it is easy to read.

Results Plus: Examiner TipTry to write as clearly as possible.

Results Plus: Examiner CommentsThough 'less negative' is incorrect, justification marks could still have been scored. If it had been clear that the iodide ion was polarized a mark could have been given, though the final statement is worrying, iodide ions are polarized because of their relatively large size. A small charge makes them less polarizable.

Results Plus: Examiner TipBe clear in the selection and use of terms like atom, molecule and ion and only give additional information if it is correct.

(e)In spite of direction in past examiners' reports and the clear direction in the previous part of the question, the phrase 'less negative' was rarely seen. Less, more increase and decrease in electron affinity were seen with almost equal frequency.

Candidates need to remember that such descriptions are too vague for energy changes.

Imprecise expressions also cost marks in the reason for this change which could be awarded even if the first part was inadequate.

Statements like 'It is further from the nucleus' (rather than 'the electron...') and 'there is shielding' (rather than '...more shielding') were typical.

Q26.In (a) (i) and (a) (ii), many candidates were able to give the correct electronic configurations, although 1p and 2d sub-shells were occasionally seen. In (b) (i), the formulae of the species were often correctly given, but there was some confusion over which state symbols to use. In (b) (ii), the majority of candidates knew that the bonding in magnesium chloride was ionic. Part (b) (iii) proved to be more challenging, with a significant number of answers showing the bonding in magnesium chloride as covalent rather than ionic. Candidates who did not read the question carefully drew only the outer shell electrons on the magnesium and chloride ions, instead of all the electrons in each species.

Quality of Written Communication was thoroughly tested in (d). Many candidates confused the process of melting with that of ionization, with answers referring to the removal of electrons from a magnesium atom frequently being seen. Answers which attempted to consider the metallic bonding in magnesium and sodium often overlooked the difference in ionic radii of the magnesium ion compared with that of the sodium ion.

Q1. A

Q2. D

Q3. A

Q4. C

Q5. C

Q6.

Question Number Correct Answer Reject Mark

C 1

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Q14.

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1 6 a i Ionic Bonding 1

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