Question

number of formula units of unit cell of MgO(rock salt), ZnS(zinc blender) and Pt(FCC) respectively
(Please explain)​

Answer 1

Electrostatic force of attraction holds the cations and anions together and forms an ionic compound.

Formula units are empirical formula of any ionic compound used for stoichiometric calculations.

The number of formula units present in the following are,

Compound                           Type                         No. of formula Units

MgO                                     Rock salt                              4

ZnS                                      Zinc blender                          4

Pt                                             FCC                                   4