# Do only metals form ions?

Do nonmetals form ions? I am asking this because I was reading something and I came across the phrase "metal ions," which left me to wonder whether or not there are nonmetal ions as well.

• Welcome to chemistry.SE! If you had any questions about the policies of our community, please ‎visit the help center. || There are a lot of nonmetal ions. The book may wanted to separate the two because the metals usually form cations. – M.A.R. ಠ_ಠ Aug 27 '15 at 21:54

In short, yes. Single-element ions are common for both metals and non-metals. Some simple examples: $\ce{F^{-}, Cl^{-}, I^{-}, S^2-}$ Multi-element non-metal cations are a bit more common: $\ce{NH4+}$ and $\ce{H3O+}$ being the obvious examples and there are plenty of anions like $\ce{CN-}$, $\ce{SO4^{2-}}$, $\ce{NO3-}$, etc. Things like proteins and polypeptides are also frequently ions in solution and may be positively or negatively charged depending on the pH.