(i) Use this information to deduce a value for Avogadro constant. (ii) Draw up a table showing the numbers and distances from P of the sodium ions in positions similar to ion A, the chloride ions in positions similar to ion B and the sodium ions in positions similar to ion C. Hence find an expression in terms of the inter-ionic distance d for the electrostatic potential energy Ves of the chloride ion P due to all other ions in this part of the crystal. (iii) The expression obtained for Ves approximates to the electrostatic potential energy of the ion P in the whole crystal. Given that the distance d in sodium chloride is 2.8E-10m, estimate the binding energy of one mole of sodium chloride. Attempt: (i) Okay I really don't know what to do over here. I can't compare the ratio of the cubic volume of NaCl with that of 12C, and neither can I compare the number of atoms of NaCl in a volume of 24dm3 or 22.4. Comparing the mass doesn't help either. Can anyone please give me some pointers on this? Thank you!