1. Naming Ionic Compounds
To review:
Ionic compounds are compounds formed when two or more elements combine chemically in an ionic bond. As you may remember, an ionic bond is the force that holds a positive ion, called a cation, to a negative ion, called an anion.
Which element forms the cation in the bonding pair on the right?
The sodium forms the positively charged cation by losing an electron.
Which element forms the anion and how?
The chlorine gains that electron that sodium gave up, making it negative.

2. Naming Ionic Compounds
An ionic bond is the strongest of the chemical bonds and it forms when two elements with widely varying electronegativities combine. Because the ions hold so tightly together, ionic compounds tend to be hard. In fact, they are crystals with high melting and boiling points, because they have a high lattice energy. Write down “lattice energy” and look it up.

3. Naming Ionic Compounds
Generally speaking, an ionic bond forms when a metal from the left side of the periodic table of elements joins with a nonmetal from the far right side. For instance, any alkali metal or alkaline earth metal will form an ionic bond with any halogen or oxygen group member.

4. Naming Ionic Compounds
Today you will learn to name ionic compounds.
Some ionic compounds are made from monatomic ions only. NaCl, sodium chloride, is made from two monatomic ions. What are they?
They are the sodium ion and the chloride ion.

5. Naming Ionic Compounds
To name an ionic compound, name the cation, then the anion with –ide or its polyatomic ion ending.
Remember: the cation, which is the metal, keeps its full name.
The anion, which is usually a halogen or an oxygen group element, gets the suffix –ide, if it was just a single atom.

6. Naming Ionic Compounds
You try:
MgO is
Magnesium oxide
CaS is
Calcium sulfide
CsI is
Cesium iodide
Na2O is
Sodium oxide
Note: Names of elements and compounds do NOT get capitalized, unless they begin sentences or other formatting issues are in play.

7. Naming Ionic Compounds
Polyatomic ions work pretty much the same, but you need to know your polyatomic ions, or at least know where to find a list of them.
A polyatomic ion is an ion made from more than one atom. It’s essentially a molecule that has gained or lost electrons.

8. Naming Ionic Compounds
NH4+ is the most common polyatomic cation. It’s name is ammonium. If it is not on your list of common polyatomic ions on the back of your periodic table of elements, add it.
OH- is hydroxide. Note that the name ends in –ide. Most polyatomic ions do not end in –ide. Look at your list of common polyatomic ions. What two suffixes are most common?
NH4OH is ammonium hydroxide. Because the positive charge of the cation was balanced out by the negative charge of the anion, no charges appear in the formula.

9. Naming Ionic Compounds
You try:
CaOH is
Calcium hydroxide
NH4CO3 is
Ammonium carbonate
Mg3(SO4)2 is
Magnesium sulfate – Notice that in that formula, three magnesium ions combined with two sulfate ions – and that tripling the sulfate ions required the use of parentheses. You will be writing chemical formulas soon!