# An ionic compound dissociates into 3 ions of 3 different elements?

When an ionic compound dissolves in water and becomes ions.

1) Typically we see:

$\ce{AB ->}$ Ions $\ce{A+ + B-}$

$\ce{ABC ->}$ Ions $\ce{AB+ + C-}$

2) But how about the one below, is there any case that will fit the situation

$\ce{ABC2 -> A+ + B+ + 2C-}$

or $\ce{AB2C-> A+ + 2B+ + C^3-}$

Yup, they are definitely possible. Such salts are called as mixed salts. They furnish more than two ions when dissolved in water. A popular example is Mohr's salt, popularly used as a standard titrant to measure concentrations of oxidizing agents. It's (anhydrous) formula is:

$$\ce{Fe^{II}(NH4)2(SO4)2}$$

This salt on dissolving in water would split as:

$$\ce{Fe^{II}(NH4)2(SO4)2 <=>> Fe^2+ + 2NH4+ + 2SO4^2-}$$

This is one such example. There are many others, notably alums. Alums are a general type of mixed salts, of the form:

$$\ce{A^{I}M^{III}(SO4)2}$$

where $\ce{A^{I}}$ is a monovalent metal ion, and $\ce{M^{III}}$ is a trivalent metal ion. Clearly, these are also mixed salts.

These are just a few practical examples. There's literally quite nothing that can stop imagination of course.

Another is the de-icing compound calcium magnesium acetate, $\ce{CaMg2(C2H3O2)6}$ (https://en.m.wikipedia.org/wiki/Calcium_magnesium_acetate). Like all such "double cation salts", this compound has a crystal structure with two different sites for cations; in this case one kind of site has the calcium ions and the other has the magnesium ions. This combination enables a reproducible stoichiometry, but when the crystal structure is broken down by dissolving the salt you just have "ion soup".