How do we know what names to call different ionic compounds? In chemistry, there are different types of ionic compounds.
In this lesson, we will go over these types and the rules we must follow to name them correctly.
What Are Ionic Compounds?
A compound forms when two or more atoms of different elements share, donate, or accept electrons. We are going to focus our attention on ionic compounds. We encounter many ionic compounds every day, like sodium chloride, which is table salt, and sodium fluoride, which is found in toothpaste.Ionic compounds, just like the name suggests, are made of ions, which are charged particles formed when electrons are transferred between atoms of different elements. The ions that make up an ionic compound are a cation, which is a positive ion, and an anion, which is a negative ion.For instance, sodium chloride is made of a cation (Na+) and an anion (Cl-).
Another ionic compound, magnesium hydroxide, is made of a cation (Mg2+) and an anion (OH-). These examples are shown here:
How do we know that the ionic compound NaCl is called sodium chloride, and Mg(OH)2 is magnesium hydroxide? In this lesson, we will learn how to name ionic compounds.
Naming Ionic Compounds
In science, it is important to have a system that we can follow in naming things.
For instance, in biology, there are rules that scientists follow in naming species. In chemistry, there are rules we must follow in naming ionic compounds. There are different types of ionic compounds, but the general rules in naming them are:
- Identify and name the cation
- Identify and name the anion
Binary Ionic Compounds
When we think of the word ‘binary,’ we think of the prefix ‘bi-,’ which means ‘two.’ Binary ionic compounds, just like the name suggests, only have two atoms from different elements; one atom is a metal, and the other atom is a nonmetal. How do we know which element is a metal and which is a nonmetal? We can tell this from its position in the periodic table.
The elements at the left side of the stairs outlined in black are metals, and those on the right side of the stairs are nonmetals.
Some examples of binary ionic compounds are shown here:
How do we name binary ionic compounds? We follow the same general rules we just mentioned:
- Identify and name the cation; the cation is the metal.
- Identify and name the anion, and change the suffix to -ide; the anion is the nonmetal.
Let’s use aluminum fluoride as an example. The cation is aluminum. The anion is the nonmetal, so, for aluminum fluoride, the anion is fluorine, so we change the suffix of that to -ide. Then it becomes fluoride. Here are other examples of binary ionic compounds and their names:
Transition metals can form more than one cation. For instance, the transition metal chromium has two ions: Cromium2+ and Cromium3+. Other examples of transition metals with two cations are shown in this table:
When naming ionic compounds containing polyatomic ions, we follow the same general rule:
- Name the cation first; this can be a metal or a polyatomic cation.
- Name the anion second; this can be a nonmetal, and if this is the case, change the suffix of the nonmetal to ‘-ide.’ However, it can also be a polyatomic anion, so we just use the name of polyatomic anion specified in the table shown here.
Here are some examples of naming ionic compounds containing polyatomic anions:
Ionic compounds are made of a cation (positive ion) and an anion (negative ion). When naming ionic compounds, we follow the general rules:
- Identify and name the cation; this is a metal element or polyatomic cation.
- Identify and name the anion; this is a nonmetal element. Change the suffix to ‘-ide,’ or use the polyatomic anion name.
There are different types of ionic compounds, so when naming them, we follow the steps outlined in this flowchart: