INTRODUCTION AND DEFINATION "The distance between the centre of of the nucleus of an ion and the point upto which the nucleus has influence on its electron cloud." The limit of electron cloud around nucleus cannot be determined with certainty. The radius of an ion is determined by determining the internuclear distance in an ionic compound by X-ray measurements. This distance is then taken as the sum of the radii of the two ions involved. "If we know the radius of one ion, we can calculate the radius of the other". "The atoms change into the ions either by the loss or gain of electrons". "A cation is always smaller than the corresponding atom ,whereas anion is always bigger than the corresponding atom". VARIATION OF IONIC RADII IN A GROUP:- Since the atomic size increases as we move down the group , therefore, ionic radius also increases in moving from top to bottom in a group. Example:- ionic radii of alkali metals may be represented as: A...
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