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.
Start by making a vertical slice through the formula just after the metal or ammonium:
Determine the ions and their charges on each half. This is definitely the tricky part. Seven rules here are helpful:
Rule 1: Group 1 metals (Li Fr) are all 1+
Rule 2: Group 2 metals (Be Ra) are all 2+
Rule 3: Aluminum is 3+; Ammonium is 1+
Rule 4: All other metals require a Roman numeral
Rule 5: Group 7 nonmetals (F I) are all 1
Rule 6: Group 6 nonmetals (O Te) AS ANIONS are usually 2
Rule 7: The overall charge must be 0
Then name those ions:
|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.
A few more tips may be helpful:
There's no way around memorizing element names. Just do it.
Rule 7 is far more valuable than most beginners realize.
Can't remember or figure out the charge on the cation? Figure it out for the anion and make it all add up to 0.
Stuck because you have a transition metal, such as Fe or Mn, and can't remember the charge on the anion? Look around for other examples of the anion being used. For example, say you have to name FeSO4 and you can't remember the charge on SO4. If you find "Na2SO4" somewhere else on the exam, quiz, or in the book, you're home free. With this information you'll know that SO4 must be 2, and therefore the charge on Fe must be 2+.
If you know your strong acids, then you know "H2SO4." H here is H+, and the overall charge is 0. So SO4 must be 2. Similarly,
HClO3 gives ClO3, and
HClO4 gives ClO4.
This works with weak acids, too, if you can remember them, such as H2CO3 and H3PO4.
Learn lots of acid names, because they help here.
X-ic acids give X-ate anions (sulfuric/sulfate, nitric/nitrate)
X-ous acids give X-ite anions (nitrous/nitrite)
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!
YOU CAN DO IT!