For crystal sodium chloride, state
(i) the type of lattice in which it crystallises.
(ii) co-ordination number of each sodium ion and chloride ion in the crystal lattice.
(iii) number of sodium and chloride ions present in a unit cell of sodium chloride.
(iv) the structural arrangement of sodium chloride crystals.

Explanation

(i) Sodium chloride crystallises in expanded face centred cubic arrangement also known as cubic close packed arrangement.
(ii) Co-ordination number of `Na^(+)` and `Cl^(-)` ions are in the ratio `6:6`.
(iii) Unit cell of NaCl has four `Na^(+)` and four `Cl^(-)` ions.
(iv) The structural arrangement of sodium chloride crystals is octahedral.