# Knowing the charge of polyatomic anions [duplicate]

I have an exercise and I have to find the formula of those ions:

• Arsenate ion
• Perbromate ion
• Selenite ion
• Hydrogen Tellurate ion

The solution tells: $\ce{BrO4-,\space SeO3^{2-}, AsO4^{3-}, HTeO4^{-}}$.

My question is, how do I get to those results and how do I know their charge to be 1-, 2-, 3-, and 1-?

• Can you amend your post to include the work you've done to solve the problem? As it stands, it looks a lot like homework and might be closed by the community here as such. – Todd Minehardt Nov 17 '16 at 15:59
• No. It is not a homework. the book I am using is Chemistry, The central science 13th edition by Theodore L. Brown. It is the exercice number 2.107 on page 79. When looking at the solution at the back of the book, I got the answers I wrote above. I do not understand though, why the respective charges of the ions are like so – billyandriam Nov 17 '16 at 16:03
• I could not understand it though. I am a first year student – billyandriam Nov 17 '16 at 16:52