## Ions, precipitates, gases, and oxidation states

Write ion charges with `^`, use `v` for a precipitate and `^` after a species for a gas. Oxidation states can be written in parentheses as ordinary text.

```mhchem
Ba^2+(aq) + SO4^2-(aq) -> BaSO4(s) v
```

```mhchem
2H2O2(aq) ->[MnO2] 2H2O(l) + O2(g) ^
```

```mhchem
Fe^3+ + e- -> Fe^2+
```