Verified answer

ok first look at your period table

from left to right -> the ionic radii is decreasing

from top to bottom the ionic radii is increasing

so when an element have a negative charge (anion) on the top which mean it is gain an electron

so it is going to be bigger with the one with positive charge (cation)

the number of cation show how much electron it have lose. so the radii size is decreasing

hope this help