The electronic configuration of given ions are as follows: K19=2,8,8,1K+=2,8,8 Ca20=2,8,8,2Ca2+=2,8,8 P15=2,8,5P3−=2,8,8 S16=2,8,6S2−=2,8,8 Cl17=2,8,7Cl−=2,8,8 As the effective nuclear charge increases from P to Ca, the atomic size decreases in the same order. Order of ionic radii