Final answer:
The ionic radius of a Na+ ion is 0.000116 millimeters.
Step-by-step explanation:
The ionic radii of ions are given in picometers (pm), which is equal to 10-12 meters. To convert the ionic radius of Na+ from picometers to millimeters, we divide the value by 106. The equation would be: 116 pm ÷ 106 = 0.000116 mm.