Which among the following elements has the largest atomic radii?

Na and Mg belong to same period whereas Na and K are in the same group. Atomic radius increases in a group and decreases in a period. Potassium (K) has the largest atomic radii (243 pm). Sodium (Na) has 190 pm. Magnesium (Mg) has 145 pm. Calcium (Ca) has 194 pm.