Naming Salts (Ionic Compounds)

Salts are ionic compounds which, when dissolved in water, break up completely into ions. They arise by the reaction of acids with bases, and they always contain either a metal cation or a cation derived from ammonium (NH4+).

Examples of salts include NaCl, NH4F, MgCO3, and Fe2(HPO4)3.

Salts are named by listing the names of their component ions, cation first, then anion. This involves three distinct steps.

Step 1: Split the Formula in Two

Start by making a vertical slice through the formula just after the metal or ammonium:

Fe2(HPO4)3 Fe2|(HPO4)3

Step 2: Determine the Charges On the Ions

Determine the ions and their charges on each half. This is definitely the tricky part. Seven rules here are helpful:

For example:

NaClNa|Cl Na+|Cl
MgCO3 Mg|CO3 Mg2+|CO32–
Fe2(HPO4)3 Fe2|(HPO4)3 Fe3+|HPO42–

Step 3: Name the Ions

Then name those ions:

NaCl Na+|Cl sodium chloride
NH4F NH4+|F ammonium fluoride
MgCO3 Mg2+|CO32– magnesium carbonate
Fe2(HPO4)3 Fe3+|HPO42– iron(III) hydrogen phosphate

Those ions, by the way, are called the principal species in solution for the salt. Figuring out the principal species in solution just this way gets to be REALLY important when you study equilibrium. You'll need to know those charges too, so you might as well learn them now and get it over with.

Tips for Success

A few more tips may be helpful:


The key to remember is that the system is designed to be unambiguous. We must be able to get one and only one formula from a name, and that name should be a standard one rather than some cutesy name like nutrasweet.

In summary, memorize the more common element names and symbols, memorize the seven rules, have a periodic table handy, learn lots of acid names and formulas, and practice, practice, practice!