Final answer:
The periodic table can predict the charge of ions formed by main-group elements; group 1 and 2 form cations with a charge equal to their group number, whereas groups 16 and 17 form anions with negative charges. Transition metals can have variable charges.
Step-by-step explanation:
The location of an element on the periodic table can help determine the likely charge of the ions it forms. Main-group elements tend to form cations with a positive charge equal to their group number when moving from the left to the right. For example, group 1 elements (alkali metals) form 1+ ions, and group 2 elements (alkaline earth metals) form 2+ ions. Conversely, when moving from the right towards the left, elements often form anions with a negative charge, equal to the number of groups moved from the noble gases. Thus, group 17 elements (halogens) form 1- ions, whereas group 16 elements form 2- ions. However, the predictive value of this trend decreases toward the center of the table, where transition metals such as copper and iron may exhibit variable charges not readily predictable by their location alone.