Atomic Structure Mark Scheme 2 Level IGCSE(9-) Subject Chemistry Exam Board Edexcel IGCSE Module Double Award (Paper C) Topic Principles of Chemistry Sub-Topic Atomic Structure Booklet Mark Scheme 2 Time Allowed: 57 minutes Score: /47 Percentage: /00 Grade Boundaries: 9 8 7 6 5 4 3 >90% 80% 70% 60% 50% 40% 30% 2 20% 0%
Expected Answer Accept Reject (a) M both protons = 6 Ma rks (b) M2 C-3 has 7 and C-4 has 8 (neutrons) same electronic configuration(s) / structure(s) OR different of protons same of electrons OR amount for / six electrons have four/same of electrons in outer / valence shell IGNORE same of electrons in inner shells IGNORE references to atomic / same of protons / different of neutrons (c) (i) M the average / mean mass of an atom (of the element) average/mean of: atomic masses / mass s / mass of isotopes mean mass of an element M2 compared to / relative to (/2 th ) the mass (of an atom) of carbon-2 OR on a scale where carbon-2 has a mass of 2 / compared with the mass of carbon-2 which is 2 M mass of one mole of atoms M2 compared to (mass of) /2 th one mole / g of carbon-2 mass of one mole of the element
c (ii) M (2 x 98.9) + (3 x.) M2 00 Expected Answer Accept Reject (2 x 0.989) + (3 x 0.0) for first 2 marks Mar ks M3 2.0 IGNORE units 2.0 on its own for 2 marks 2.0 on its own for 3 marks
Answer Notes Marks 2 (a) electron(s) (b) electron(s) (c) (i) protons (and) electrons Accept in either order both answers (ii) protons neutrons (d) (i) 2 (ii) 24 (iii) 2.8.2 Accept any other punctuation marks, such as, / ) and no punctuation marks Total 8 marks
Answer Notes Marks 3 (a) 3 (b) ammonia / NH 3 Do not accept ammonium hydrogen chloride / HCl Do not accept hydrochloric acid Accept in either order. If name and formula given, both must be correct. Ignore state symbols, except HCl (aq) (c) ammonium chloride / NH 4 Cl Do not accept ammonia chloride. If name and formula given, both must be correct. (d) cross in box 2 (decomposition) cross in box 4 (neutralisation) Total 6 marks
Answer Notes Marks 4 a b i A (an electron) ii B (a neutron) iii B (electrons and protons) c isotopes atomic s mass s 3 Total 7 marks
Mark Answer Accept Reject s 5 (a) releases thermal energy releases heat (energy) just releases energy (b) produces an increase in temperature (c) D (d) A M (consists of) positive AND negative/oppositely charged ions/mg 2+ AND O 2 (ions) IGNORE references to loss and gain of electrons 4 M2 (strong) attraction between (positive AND negative/ oppositely charged) ions/mg 2+ AND O 2 (ions) (strong) ionic bonding/(strong) ionic bonds M3 many ions (present in lattice)/giant structure/giant lattice M4 large amount of energy required (to separate the ions/overcome the attraction between the ions) If mention of covalent bonds/metallic bonds/intermolecular forces only M4 can be awarded 7 (e) M (name) magnesium chloride M2 (formula) MgCl 2 Penalise inappropriate use of upper or lower case letters or s in the wrong place break the ionic bonding/bonds accept a correct formula as a product in an equation whether the equation correct or not Total 9
Answer Notes Marks 6 a M nucleus M2 protons Accept in either order M3 neutrons M4 electrons M5 shells M6 protons AND electrons In either order M7 electrons b i 3 ii 5