Question

What is packing efficiency?

Answer 1

when molecules form a structure they occupy some area in the space but molecules are sphere when they are stacked on one another there is some gap between two adjacent molecules due to which
actual volume of the molecules with out any gap and molecules volume with gap
ratio of these two is packaging efficiency
mathematically if
molecules are packed in cube of side a
each molecules have radius r
total molecules =n
packaging efficiency=n*4/3*pi*r^3/a^3

Answer 2

Packing efficiency:- It can be defined as as ratio of the total volume utilised to the atoms of the total volume of the crystalline substance. It is also known as packing fraction.

$\sf{Packing \: Efficiency = \frac{Volume \: occupied \: by \: atoms \: in \: a \: crystal }{Volume \: of \: the \: crystal}} \\ \\ \sf{ \large{or}} \\ \\ \sf{Packing \: Efficiency = \frac{Volume \: occupied \: by \: atoms \: present \: in \: unit \: cell}{Volume \: of \: the \: unit \: cell}} \\ \\ \sf{\large{or}} \\ \\ \sf{\sf{Packing \: Efficiency = \frac{z \times \frac{4}{3}\pi {r}^{3} }{v}}}$

where,

z = number of atoms present in the unit cell or number of formula units for ionic crystal.