structure

• y does diamond have a higher melting temperature than iodine? [5]

  This is coz:

  • Iodine is simple molecular; [1 mark]
  • Diamond is a giant covalent lattice structure, with 4 covalent bonds per carbon atom; [1 mark]
  • Iodine molecules are held together by weak London forces; [1 mark]
  • Carbon atoms in diamond are held together by strong covalent bonds; [1 mark]
  • Strong covalent bonds require more energy to break than intermolecular forces; [1 mark]
• Describe the key feature of the bonding of the carbon atoms in graphite that results in it being an electrical conductor [3]

  • The carbon atoms are arranged in layers, allowing the flow of electricity through them; [1 mark]
  • One delocalised electron within the layer to carry the current is mobile & free to move; [1 mark]
  • And each carbon is covalently bonded to three other carbons; [1 mark]
• what is the reason for the shortest bond in methanol? [1]

  O-H (NOT -O-H) The reason why this is the shortest bond is because the electronegativity between the oxygen and hydrogen atoms is the greatest in the molecule
• what is the strongest type of intermolecular force that occurs between molecules of methanol and water? [1]

  hydrogen bonding  
• how do London forces form between halogen molecules? [3]

  • There is an uneven distribution of electrons; [1 mark]
  • This results in an temporary oscillating dipole in the first molecule; [1 mark]
  • Which induces a second dipole on the adjacent molecule; [1 mark]
• y does Bromine have a higher boiling temperature than chlorine? [2]

  • Bromine has more electrons than chlorine; [1 mark]
  • Therefore, bromine has more London forces between molecules; [1 mark] 
• The experiments and the expected observations to determine the order of reactivity of Bromine, Iodine, KCl, KBr and KI (halogens) using the smallest number of experiments are: [5]

  Experiment 1:

  • Mix bromine with potassium chloride; [1 mark]

  Experiment 2:

  • Mix bromine with potassium iodide; [1 mark]

  Number of experiments:

  • Only two experiments as above used; [1 mark]

  Colours of halogen in cyclohexane:

  • Experiment 1 = bromine is orange / yellow AND Experiment 2 iodine is purple / pink / violet / lilac; [1 mark]
• Explain the shape of a PCl3 molecule [3]

  • PCl3 is trigonal pyramidal; [1 mark] 
  • Has 3 bond pairs & 1 lone pair around its central P atom; [1 mark] 
  • And electron pairs repel to positions maximum separation; [1 mark] 
• y does phosphorus form PCl5, but nitrogen does not form NCl5? [2]

  • Phosphorus can expand its octet, accommodating more than 8 electrons to 10 electrons as it has available 3d-orbitals for promotion of electrons; [1 mark] 
  • Whereas, nitrogen does not have 2d-orbitals, therefore can only accommodate eight electrons in its outer shell; [1 mark] 
• NSDAE stands for?

  
  

  • Nuclear charge/no. of protons
  • Shielding/no. of shells
  • Distance between outer shell electrons & the nucleus (atomic/ionic radii)
  • Attraction between the nucleus & outermost electron
  • Energy required to gain/lose an electron
• explain the 1st ionisation energy experiences across a period in terms of NSDAE

  • The nuclear charge/no. of protons increase
  • Shielding/no. of shells stays the same
  • Distance between outer shell electrons & the nucleus decreases
  • Attraction between the nucleus & outermost electron increases,
  • therefore so does the energy required to gain/lose an electron
• explain what halides experiences going down group 7 in terms of NSDAE

  • The nuclear charge/no. of protons increase
  • Shielding/no. of shells also increases
  • Distance between outer shell electrons & the nucleus increases
  • Attraction between the nucleus & outermost electron decreases,
  • therefore so does the energy required to gain/lose an electron