Question

The ratio of r+:r- is 0.42 the co-ordination of cation is

Answer 1

Field of science i.e. inorganic chemistry cation-anion radius ratio is the ratio of ionic radius of cation with respect to ionic radius of anion in cation-anion compound isnormally shown by {\display style r_{C}/r_{A}}  

As per Pauling's rules for crystal structures allowed size of cation in a given structure is confirmed by critical radius ratio.