Final answer:
For elements in groups 13-17, the cation charge equals to the group number minus 10; for instance, group 13 elements form 3+ cations.
Step-by-step explanation:
The charge of the cation formed by the loss of all valence electrons for elements in groups 13-17 is equivalent to the group number minus 10. This is because elements in these groups have their group numbers exceeding the number of valence electrons by 10, which includes potential fully-filled d subshells for elements in higher periods. Therefore, for example, aluminum, which belongs to group 13, will form a cation with a charge of 3+ (Al³+), after losing all its valence electrons.