Answer:
Mg²⁺ cation
Br⁻ anion
Step-by-step explanation:
Magnesium is present in group two of periodic table.
It is alkaline earth metal.
It has two valance electrons.
Thus by losing two valance electrons it complete the octet. The common oxidation state of magnesium is +2.
The bromine is present in group seventeen.
It has seven valance electrons.
It is the member of halogen family.
To complete the octet bromine required one electron. By gaining the one electron it showed -1 oxidation state.
When bromine combine with magnesium both formed MgBr₂.
The one atom of Mg have +2 oxidation state while bromine have -1 that's why to make the overall compound neutral two bromine atoms combine with one atom of magnesium.