(Multiple choice) Which one of the following statements is true? Explain (a) In NaCl, the choice of which interstices are occupied by Cl- is dictated by the relative sizes of Na+ and Cl- (b) In MgO, the choice of which interstices (sites) are occupied by the magnesium anions is dictated by the relative sizes of the anions and cations. (c) In the unit cell of FeO, the number of tetrahedral interstices is two times the number of octahedral interstices. (d) In the unit cell of FeO, the number of nearest neighbor atoms surrounding a tetrahedral interstice is one half the number of nearest neighbor atoms surrounding an octahedral interstice. (e) Wear-resistant dies are often made from polycrystalline diamond, WC, and cement Solution A,B,C,D are wrong but figure E is true. For more clarification visit this article it\'s totally answer your questions. http://employees.oneonta.edu/viningwj/chem112/Chapter_12_Solids_RD_for_class.pdf some asnwers from the same link +Because a tetrahedral hole is smaller than an octahedral hole, which in turn is smaller than a cubic hole, relative size can dictate the type of vacancies that are filled in a lattice and this can dictate the type of lattice formed +The binding energy in a crystalline lattice is called the lattice energy and is given the symbol U. It is the energy required to separate one mole of a crystalline ionic solid into its gaseous ions. Alternatively it can be defined as the energy released when one mole of a crystalline ionic solid forms from its gaseous ions. For example, for NaCl +Advantages of diamond grinding tools Diamond can be used to make grinding tools, which have following advantages: .