Edexcel Jun 2016 (IAL) Paper 1 Q (with explained solutions) |

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Edexcel Jun 2016 (IAL) Paper 1 Q

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18 This question is about the elements aluminium and magnesium. (a) Complete the electronic configuration for an atom of aluminium. (1) 1s2(b) Complete the table to show the composition of an aluminium ion, Al3+. (1) Subatomic particle Number of particles in Al3+ proton neutron electron (c) The table below shows the first four ionization energies of aluminium. (i) Complete the table by identifying the orbital from which each electron is removed. (2) First ionization energy Second ionization energy Third ionization energy Fourth ionization energy Ionization energy / kJ mol1 578 1817 2745 11578 Orbital (ii) Write the equation, including state symbols, which represents the second ionization energy of aluminium. (2) A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D *P46662A01120* 11 Turn over<br />
*(iii) Explain why the second ionization energy of an element is always greater than the first ionization energy. (2)D O N O T W R I T E I N T H I S A R E A *(iv) Explain why the difference between the third and fourth ionization energies of aluminium is much larger than the difference between the first and second ionization energies. (2)(d) Aluminium is a silvery metal with a melting temperature of 933 K. (i) Draw a labelled diagram of the bonding in aluminium. (2) 12 *P46662A01220* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br />
(ii) The atomic number of magnesium is one less than aluminium. Would you expect magnesium to have a higher or lower melting temperature than aluminium? Justify your answer. (2)(iii) Draw the dot and cross diagram for magnesium chloride, MgCl2. Show the outer electrons only. *(iv) Aluminium chloride has more covalent character than magnesium chloride. Explain what this statement means. By considering the physical properties of these two chlorides, suggest one piece of evidence showing that aluminium chloride has more covalent character than magnesium chloride. (2) (3)A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D(Total for Question 18 = 19 marks) *P46662A01320* 13 Turn over<br />

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Acceptable Answers (1s2) 2s2 2p6 3s2 3p1 ALLOW Upper case, subscripts, P orbitals divided into x, y, z eg: 2s2 2px IGNORE 1s2 if written again 2 3s2 3px 1 2 2py 2 2pz Acceptable Answers protons neutrons electrons 13 14 10 All three numbers needed for mark IGNORE any working out in table Acceptable Answers First IE Second Reject Mark (1) Reject Mark (1) Reject Mark (2) Third IE 2745 3s Fourth IE 11578 2p IE 1817 3s 578 3p 3p/ 3px and both 3s (1) 2p/ 2px / 2py / 2pz (1) ALLOW p s s p for (1) mark 3p1 3s2 3s1 2p6 for (2) marks Question Number 18(a) Question Number 18(b) Question Number 18(c)(i)<br />
Reject Mark (2) Acceptable Answers Question Number 18(c)(ii) Al+ (g)Al2+(g) + e OR Al+ (g)eAl2+(g) MP1 Balanced equation (1) MP2 (g) symbols This is dependent on the equation involving aluminium even if electrons/charges are wrong (1) NOTE If correct equation for a second ionization using the wrong symbol is given with correct state symbols allow (1) max IGNORE lack of minus sign on electron / any state symbols for electron<br />
Acceptable Answers Question Number *18(c)(iii) MP1 Second electron is closer (to nucleus) / electron is removed from a positive ion / 1+ ion is smaller than atom ALLOW More protons than electrons (in ion) Effective nuclear charge greater (in ion) (1) MP2 So greater attraction between electron and nucleus/protons OR More energy required to overcome attraction between electron and nucleus OR Less repulsion between electrons (1) IGNORE References to high charge-density in 1+ ion References to shielding / last electron / paired electrons / electron shell stability Mark (2) Reject Just more energy required to remove electron / harder to remove electron NOTE Second I.E. loses 2 electrons - scores (0) overall 1+ ion has more protons than atom - scores (0) overall<br />
Acceptable Answers Question Number *18(c)(iv) MP1 for similarity between first Mark (2) Reject 1st and 2nd from same subshell and second electrons lost; 1st and 2nd (electrons are removed) from the same/3rd shell OR First (electron lost from) 3p (subshell/orbital) and second (electron lost from) 3s (subshell/orbital) MP2 for difference between third and fourth electrons lost; Third (electron lost from) 3s (subshell/orbital) and fourth (electron lost from) 2p (subshell/orbital) OR (compared with the 3rd electron) the 4th electron is removed from a shell closer to the nucleus / from a new/lower/different shell / from a shell with less shielding If no other mark awarded, allow (1) for: three electrons in the 3rd shell of Al and the fourth electron is removed from 2nd shell IGNORE References to charges on ion (1) (1)<br />
Question Number 18(d)(i) Acceptable Answers Reject Mark (2) Protons / nucleus / atoms Regular lattice of + OR 3+ (can be written in ions or labelled) ALLOW Ions which touch (1) Delocalised electrons/sea of electrons including some between ions, shown and labelled (1) Mark (2) Acceptable Answers Question Number 18(d)(ii) (Mg) lower (melting temperature) because (no mark for this alone) and any two from: (Mg) ion charge is less / (Mg) ion (radius) is larger / (Mg) ion charge density is less / (any mention of) Mg2+ and Al3+ (1) (Mg) fewer delocalised/free electrons / smaller sea of electrons / one less electron donated (1) (Mg) weaker (forces of) attraction between (+ve) ions and (delocalised/free electrons / sea of electrons) / (Mg) ions are held less tightly to the sea of electrons / metallic bond is weaker (1) Reject Mg has a higher melting point scores (0) overall Atomic radius (of Mg) is larger References to ionic bonds / covalent bonds / intermolecular forces score (0) overall<br />
Mark (2) Reject Covalent bondingscores (0) overall Question Number 18(d)(iii) Acceptable Answers First mark Correct dot and cross diagrams with 2+ on Mg and/ 1- / -1 charge on (both if drawn) Cl (1) ALLOW No electrons or 8 electrons on outer shell of Mg Dots or crosses or other valid symbols for electrons Paired or unpaired electrons Diagrams without brackets Second mark Ratio of one Mg to two Cl (ions) (1) ALLOW Number of Cl shown as 2 in front of a Cl, or as a subscript after the Cl The ratio mark even if no charges are shown (penalised in 1st mark) IGNORE any inner electrons ALLOW max 1 for incorrect symbols if charges and ratio are correct<br />
Acceptable Answers Question Number 18(d)(iv) MP1 Mark (3) Reject References to Al / Mg or Cl atoms / chlorine (Total for question 18 = 19 marks) (1) Al (cat)ion polarises chloride / distorts chloride electron cloud OR Al (cat)ion has a greater polarising ability (than Mg ion) OR Chloride ion/anion in AlCl3 is distorted (by aluminium (ion)) MP2 EITHER Electrons are partly shared (by Al and Cl) OR (In AlCl3) orbital overlap occurs OR (aluminium and chloride) ions are not totally discrete/separate (1) IGNORE fully shared electrons References to ionic size and charge References to atomic radius Ionic bond strength/stability Polarisation of AlCl3 / polarisation power of AlCl3 MP3 Melting/boiling temperature (of AlCl3) is lower (than that of MgCl2) OR (AlCl3) sublimes / Molten salt/AlCl3 does not conduct electricity / cannot be electrolysed ALLOW BH cycle / experimental LE value greater / more negative / more exothermic than theoretical LE value of AlCl3 (AlCl3) forms a dimer (AlCl3) forms dative covalent/coordinate bonds (with electron pair donors) Magnesium chloride solution is a better conductor than aluminium chloride solution (1)<br />

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