Final answer:
To neutralize an atom with a -2 charge, two +1 charged atoms, or cations, are required. Each +1 cation cancels out one unit of negative charge, leading to a neutral entity when two of them react with the -2 charged atom.
Step-by-step explanation:
If an atom has a charge of -2, it means that it has two more electrons than protons, giving it a negative charge. To achieve a neutral atom, the charge must be balanced out by introducing positive charges. If you have +1 charged atoms, also known as cations, you will need two of them to react with the -2 charged atom. This is because negative and positive charges of equal magnitude cancel each other out. So, to neutralize a -2 charge, you need a total positive charge of +2. This can be achieved by two +1 cations reacting with the negatively charged atom, resulting in a neutral species.
For example, in a compound like water (H₂O), there are two hydrogen atoms each with an oxidation number of +1, giving a total positive charge of +2, which balances with the -2 from a single oxygen atom, resulting in a neutral molecule.