Mumbai university > FE > SEM 1 > Applied Physics 1

Marks: 7M

Year: Dec 2013

Ligancy

Ligancy is defined as the number of nearest anions surrounding the central cation.

Critical Radius Ratio:- The ratio of cation radius to the anion radius in an ionic crystal for which the crystal is stable is called the Critical Radius Ratio.

Conditions for stability of ionic crystal:-

• The stability of crystal is determined by the Critical Radius Ratio.

• If the cation is too small, then it will attract the anions into each other and they will collide hence the compound will be unstable due to anion-anion repulsion; this occurs when the radius ratio drops below the Critical Radius Ratio.

• At the stability limit the cation is touching all the anions and the anions are just touching at their edges.