The ionic compound Fe Br3 is electrically neutral.
The oxydation state of Br is -1, which gives a total of 3 negative charges, when you multiply 3 ions times -1 charge.
Then the oxydation state of Fe has to be 3+.
Then the compound is formed by two charged particles, Fe+3 which is positively charged ion or cation, and Br - which is negatively charged or anion.
The algebraic sum of the charges of the ions must result 0 (neutral state).
The formulas of the ions is:
[tex] Fe^{3+} [/tex]
and
[tex]Br^{-} [/tex]
[tex]FeBr _{3} = Fe^{3+} +3 Br^{-} [/tex]
