A magnesium ion has a charge of + 2 and an oxygen ion has a charge of - 2. What is the chemical formula of the compound made of these ions?

It would be MgO because as stated in the question a magnesium ion has a charge of + 2 and an oxygen ion has a charge of - 2. The charges would cancel each other out therefore leaving each of the elements with only one of each.

The chemical formula of the compound of these ions will be: MgO

Explanation:

The chemical formula is the representation of the elements that form a compound and the proportion in which they are found. This proportion is shown by the number of atoms that make up the molecule.

The relationship with which the atoms of the elements combine to form an ionic compound is determined by the cation charges (positively charged ion) and the anion (negatively charged ion). The compounds are always electrically neutral, so ions must have a relationship so that the total number of positive charges equals the number of negative charges and adds up to zero.

The charge of the first ion (regardless of the + or - signs) gives you information about the number of atoms in the second ion and vice versa. Both chemical symbols are written starting first with metal and then nonmetal. After each of them, the number of atoms in the form of a subscript must be written. So, for ionic compounds to be electrically neutral, if the charges of cations and anions are numerically different, the following rule applies: the cation subscript must be numerically equal to the anion charge, and the anion subscript must be numerically equal to the charge of the cation. If the charges are numerically equal, it is not necessary to put subscripts, because in both cases the subscript will be 1. This rule is derived from the fact that the formulas of the ionic compounds are their empirical formulas. The empirical formula is the simplest expression to represent a chemical compound and indicates the elements that are present and the minimum proportion in whole numbers between its atoms.

In this case, since the charges are numerically equal, the chemical formula of the compound of these ions will be: MgO