What is the relation between the radius, co-ordination number and the structural arrangement of the molecule?
Answers
Answer: In ionic crystals the positive and negative ions are held together with coulombic forces . A crystal structure is determined by the ratio of ionic radii of its components . This ratio coordinates the coordination number of the smaller ions. In ionic crystals each ion is surrounded by definite number of the oppositely charged ions. The number of the nearest neighbour is the coordination number of the central ion. This number depends upon the radii of the ions and radius ratio of the two ions.
The ratio of the radii of the positive and negative ions is called the limiting radius ratio.
Limiting radius ratio = Radius of cation / Radius of anion = r + / r –
‘ The effect of radius ratio in determining the coordination number and shape of the ionic crystal is known as radius ratio effect.’
On the basis of Limiting radius ratio ,we can say about coordination number and shape of the ionic crystal.
Explanation: