Final answer:
The charge of a monatomic element is determined by its group on the periodic table with metals forming positive cations and nonmetals forming negative anions based on their group number.
Step-by-step explanation:
The charge of a monatomic element of a representative element can be determined by its position on the periodic table. Metals, such as alkali metals in group 1, form cations with a positive charge equal to their group number, giving them a 1+ charge. Alkaline earth metals in group 2 form cations with a 2+ charge. Transition metals can have variable charges, which are not predictable by their group number. Nonmetals in groups 14 to 17 tend to form anions with a negative charge, calculated as the group number minus eighteen. For example, halogens in group 17 form anions with a 1- charge, while oxygen in group 16 forms anions with a 2- charge.