Prior Knowledge Answers

Prior knowledge Answers Test yourself (page 2) 1 The more reactive metal displaces the less reactive metal from its compound, e.g. Zn(s)CuSO4(aq) → ZnSO4(aq) + Cu(s) 2 A metal or hydrogen 3 Carbon dioxide is produced. acid + carbonate → metal compound (salt) + carbon dioxide + water 4 They are all white crystalline solids. Test yourself (page 6) 5 Oxides of nitrogen split into oxygen and nitrogen on heating. Any ionic salt, such as sodium chloride or aluminium oxide, can be split into elements by electrolysis when molten. 6 Test yourself (page 7) 7 a) H–Cl , HCl b) S=C=S, CS2 8 a) Hydrogen and sulfur, H2S b) Chlorine and oxygen, Cl2O c) Hydrogen and nitrogen, H3N or more usually NH3 © Andrew Hunt, Graham Curtis, Graham Hill 2019 Prior knowledge Answers Test yourself (page 8) 9 a) Copper, steel b) Salt, limestone c) Ice, sugar 10 a) C2H6O2 b) CH3O 11 Because Al(OH)3 contains one Al atom combined with 3 O atoms and 3 H atoms, whereas AlOH3 would contain one Al atom combined with only one O atom and 3 H atoms. 12 a) K2SO4 b) Al2O3 c) PbCO3 b) PbCO3 b) Fe2(SO4)3 Test yourself (page 9) 13 Molecules a) Copper, steel c) Salt, limestone e) Ice, sugar Ions b) copper (i) oxide d) lithium fluoride 14 Test yourself (page 10) 15 a) CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) b) 16 a) H2(g) + Cl2(g) → 2HCl(aq) b) Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) c) 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(l) d) 2Fe(s) + 3Cl2(g) → 2FeCl3(s) Test yourself (page 11) 17 a) Zn(s) + 2HCl(aq)→ ZnCl2(aq) + H2(g) b) CaO(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) c) KOH(aq) + HCl(aq) → KCl(aq) + H2O(l) © Andrew Hunt, Graham Curtis, Graham Hill 2019 Prior knowledge Answers d) ZnCO3(s) + 2HCl(aq) → ZnCl2(aq) + CO2(g) + H2O(l) 18 a) Potassium nitrate b) Calcium chloride c) Copper(ii) sulfate d) Copper(ii) sulfate © Andrew Hunt, Graham Curtis, Graham Hill 2019 1 Atomic structure and the Periodic Table Answers Test yourself (page 13) 1 a) The third and fourth points are still thought to be correct. b) The first point is incorrect because atoms can be split into smaller particles. The second and fifth points are incorrect because of the existence of isotopes. 2 a) H2O, CO2, CuO b) c) Water Test yourself (page 15) 3 a) Most of the atom is empty space, so most alpha particles miss the small central nucleus. b) Some positive alpha particles pass near a positive nucleus, which repels them and causes them to be deflected from their original path. c) A few alpha particles approach positive nuclei of the gold atoms ‘head-on’ and are repelled backwards, so they appear to rebound from the foil. 4 a) They must be very small, occupying relatively little space. b) Thomson’s plum pudding model suggested a more solid structure for atoms with little or no empty space. This would not have produced the scattering of alpha particles which Geiger and Marsden observed. 5 Scientists publish their work so that their results and interpretations can be checked by other scientists before being accepted as reliable new knowledge. This process of peer review adds support to valid claims; it also helps to detect false results that cannot be repeated and to test new theories. Scientists also compete to be the first to publish new discoveries. Test yourself (page 16) 6 the hydrogen atom the helium atom (1p, 0n, 1e) (2p, 2n, 2e) © Andrew Hunt, Graham Curtis, Graham Hill 2019 1 Atomic structure and the Periodic Table Answers 7 Atomic model Evidence Discovery that compounds have a definite composition and Dalton’s solid atoms that atomic masses can be used to find formulae. Discovery of beams of negative electrons coming from many Thomson’s plum pudding different substances. Neutral atoms made up of negative model ‘plums’ in a positive ‘pudding’. Rutherford’s ‘solar Alpha particle scattering experiment suggests that the positive system’ atom charge of atoms must be concentrated in a tiny nucleus. Chadwick’s model of a nuclear atom with Uncharged particles produced by bombarding beryllium with protons, neutrons and alpha particles accounts for the relative masses of atoms. electrons Test yourself (page 17) 8 The spacing between centres of atoms is about 7 mm = 7 × 10−3 m. The magnification is times 35 × 106. The diameter of one gold atom is about 2 × 10−10 m = 0.2 nm. 9 a) 4p, 5n, 4e b) 19p, 20n, 19e c) 92p, 143n, 92e d) 9p, 10n, 10e e) 20p, 20n, 18e 16 O 10 a) 8 40 Ar b) 18 23 Na + c) 11 32S 2− d) 16 Test yourself (page 18) 11 a) 4 b) 204, 206, 207 and 208 c) 1 : 16 : 11 : 34 © Andrew Hunt, Graham Curtis, Graham Hill 2019 1 Atomic structure and the Periodic Table Answers Test yourself (page 21) 12 a) 12 b)2 c) 8 d) 3 e) 4 13 a) silicon-28: 14p, 14n; silicon-29: 14p, 15n; silicon-30: 14p, 16n b) Relative atomic mass = (.93 0×+ 28 )(. 5 0 ×+ 29 )(. 2 0 × 30 ) 100 = 28.1 14 a) The boiling temperature of neon-20 is lower than that of neon-22. Neon is a noble gas containing single atoms held together by weak intermolecular forces (here interatomic forces). On average, the energy required to separate and vaporise the lighter atoms of neon- 20 is slightly less than that for neon-22, so its boiling temperature is lower. ×+× b) Relative atomic mass of neon = (90 20 )( 10 22 ) 100 = 20.2 15 Isotopes have the same atomic number and therefore the same number of electrons and the same electronic structure. Chemical properties are determined by electronic structures, so isotopes have the same chemical properties. Isotopes have different mass numbers and therefore different masses. Physical properties, such as density, melting temperature and boiling temperature, are determined by mass, so isotopes have slightly different physical properties. Test yourself (page 22) 16 a) 71.0 b) 256.8 c) 46.0 d) 154.0 17 a) 95.3 b) 159.6 c) 249.6 18 a) 58 b) CH3CH2− and CH3CH2CH2− c) CH3CH2CH2CH3 Test yourself (page 25) 19 a) Ca+(g) → Ca2+(g) + e− b) Al2+(g) → Al3+(g) + e− 20 a) 4 © Andrew Hunt, Graham Curtis, Graham Hill 2019 1 Atomic structure and the Periodic Table Answers b) For the first ionisation energy, an electron is being removed from a neutral atom. For the second and subsequent ionisation energies, an electron is being removed from an ion with an increasing positive charge. The process of removing an electron becomes more difficult and therefore more endothermic. c) The diagram should show two electrons in a lower level and two in a higher level. d) Group 2 Test yourself (page 28) 21 The sketch graph should show the first five electrons removed at low but slowly rising values of log ionisation energy, then eight electrons at significantly higher but slowly rising values of log ionisation energy, and finally two electrons at a significantly higher value, again with the final value of log ionisation energy slightly higher than the penultimate one. 22 a) 2, 1 b) 2, 6 c) 2, 8 d) 2, 8, 4 Test yourself (page 29) 23 a) 1s22s1 b) 1s22s22p4 c) 1s22s22p6 d) 1s22s22p63s23p2 24 a) b) c) d) 25 a) helium b) carbon c) magnesium d) sulfur Test yourself (page 31) 26 a) 1s22s22p63s23p63d14s2 b) 1s22s22p63s23p63d54s2 c) 1s22s22p63s23p63d104s2 © Andrew Hunt, Graham Curtis, Graham Hill 2019 1 Atomic structure and the Periodic Table Answers d) 1s22s22p63s23p63d104s24p2 27 a) calcium b) nickel c) germanium 28 a) 1s22s22p6 b) 1s22s22p63s23p6 c) 1s22s22p63s23p63d10 d) 1s22s22p63s23p63d104s24p6 Test yourself (page 32) 29 Because they have the same number of electrons in the outermost shell. 30 Noble gases have completely filled sub-shells of electrons and, in the case of helium and neon, completely filled shells. Filled shells and sub-shells are associated with higher stability and this results in the unreactive nature of the noble gases 31 a) Fluorine: 2, 7 and 1s22s22p5; chlorine: 2, 8, 7 and 1s22s22p63s23p5 b) Both fluorine and chlorine require one electron to fill their outer shell. When metals react they give up electrons. So, fluorine and chlorine react vigorously with metals taking the electrons which metals are prepared to give up in order to fill their outer shells. c) When fluorine and chlorine react with metals, they form ions, F– and Cl− both of which have one negative charge. These ions combine with positive metal ions and form compounds with similar formulae such as NaF and NaCl, CaF2 and CaCl2. Test yourself (page 34) 32 As atomic number increases in any group of the periodic table, the nuclear charge increases (tending to increase the first ionisation energy), the diameter of the atoms increase (tending to reduce the first ionisation energy) and shielding from filled inner shells of electrons increases (tending to reduce the first I.E.). Overall, the influence of the larger diameter and increased shielding outweighs that of larger nuclear charge Activity: Mass spectrometry in sport (page 23) 1 301 2 Yes, because the relative molecular mass of dihydrocodeine (C18H23O3N) = (18 × 12) + (23 × 1) + (3 × 16) + 14 = 301 3 Relative mass of fragment lost = 17 © Andrew Hunt, Graham Curtis, Graham Hill 2019 1 Atomic structure and the Periodic Table Answers 4 The fragment lost with a relative mass of 17 could be −OH, and the fragment lost with a relative mass of 31 (leaving a fragment of relative mass 270) could be CH3O−.

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