Final answer:
The charge of the ions formed by elements in groups 1A to 3A is typically equal to the group number, with group 1A forming +1 ions, group 2A forming +2 ions, and group 3A forming +3 ions.
Step-by-step explanation:
In the table of ionic radii, for elements in groups 1A to 4A, the charge of the ions typically corresponds to the group number. For instance, elements in group 1A, such as sodium (Na) and potassium (K), tend to form ions with a +1 charge, reflecting the single valence electron they lose to achieve a noble gas electron configuration. As we move to group 2A, elements like magnesium (Mg) and calcium (Ca) form ions with a +2 charge, losing two valence electrons. Similarly, for group 3A, elements such as aluminum (Al) commonly form ions with a +3 charge. However, carbon (C) in group 4A does not typically form ionic compounds due to its covalent character. Overall, the trend shows that the charge of an ion is generally equivalent to the group number for these groups in the periodic table.