Final answer:
Predicting the charge of an ion formed by an element can often be done by using the periodic table, where main-group elements form ions with a charge equal to their group number, but transition metals may exhibit variable charges.
Step-by-step explanation:
To predict the charge of the ion formed by each element, the periodic table is an indispensable tool. Main-group elements tend to form cations with a charge equal to their group number. For instance, group 1 elements form 1+ ions, and group 2 elements form 2+ ions. Conversely, elements on the right usually form anions. Group 17 elements form 1- ions, and group 16 elements form 2- ions, with the charge being equal to the number of groups moved left from the noble gases.
However, the center of the periodic table is less predictable. Here, transition metals and some other metals might have variable charges. For example, copper can form ions with a 1+ or 2+ charge and iron can form ions with a 2+ or 3+ charge.
In summary, while elements in the same vertical column often form ions with the same charge because of their identical number of valence electrons, the exact charges can vary, especially among transition metals.