Question

why do solids generally lack the property of diffusion?

Answer 1

Diffusion is the spreading out and intermixing of one substance into another due to movement of the particles .
Diffusion is the property of Matter. It occurs in solids ,liquids and gases.

Rate of Diffusion : Gases>liquid>Solids.

The diffusion in solid is very very slow because the particles in solids do not move from their fixed positions. the particles of solids vibrate only about their mean positions.
Due to lack of movements in the particles of solids , the diffusion property is very slow in solids.
Hence solids generally lack the property of diffusion

Answer 2

The particles of solid are very tightly packed.
They have least intermolecular spaces between them.
As a result, free movement of particles does not take place in solids.
They can only move about their mean position.
Therefore solids lack the property of diffusion.
Rate of diffusion is highest in gases, as they have maximum intermolecular spaces.
The gaseous particles easily move from one place to other.
Rate of diffusion is moderate in liquids.
They also intermolecular spaces which are more than solids but less than gases.