Naming Covalent Compounds
Table of Contents
A covalent compound is made up of two or more nonmetal atoms that share electrons to form chemical bonds. These shared electrons create a covalent bond. To name these compounds in a consistent and accurate way, chemists around the world follow a system developed by the International Union of Pure and Applied Chemistry (IUPAC). We call them systematic names. [1-4]
Why Do We Need Systematic Naming Rules [3]
Using proper names for compounds helps avoid confusion, makes communication clear across the world, shows what elements and how many atoms are in a compound, helps predict how it will behave, and keeps everyone safe by preventing mix-ups between similar substances.
Now that we understand the importance of naming rules, let us explore how to apply them to binary covalent compounds, the simplest type.
Binary Covalent Compounds
These compounds are made of two different nonmetals joined by covalent bonds. They commonly include elements like hydrogen, oxygen, nitrogen, sulfur, and the halogens. [1,2,4-6]
Naming Rules
- Name the first element using its full name from the periodic table.
- Modify the second element’s name by using its root and adding the suffix “-ide”.
- Use prefixes to show how many atoms of each element are present. For instance, you could use “mono-” for one atom, “di” for two, “nona-” for nine, “deca-” for ten, and so on.
- Combine the names into one word or phrase.
Note: Drop the prefix “mono-” for the first element only.
Example
We will now work out an example. Consider the following compound: CO2
- First element: Carbon
- Second element: Oxygen → root “ox” + “ide” = oxide
- Number of oxygen atoms: 2 → prefix “di-”
- Final name: Carbon dioxide
Here are some more examples.
| Formula | First Element | Number of Atoms of the First Element | Second Element (Root + “-ide”) | Number of Atoms of the Second Element | Name |
|---|---|---|---|---|---|
| CO | Carbon | 1 | Oxide | 1 | Carbon monoxide |
| PCl₃ | Phosphorus | 1 | Chloride | 3 | Phosphorus trichloride |
| SF6 | Sulfur | 1 | Fluoride | 6 | Sulfur hexafluoride |
| CF4 | Carbon | 1 | Fluoride | 4 | Carbon tetrafluoride |
| N₂O₅ | Nitrogen | 2 | Oxide | 5 | Dinitrogen pentoxide |
Common Names vs. Systematic Names
Some covalent compounds are more commonly known by their traditional names rather than systemic names. These names were given before modern naming rules were established and are still widely used. Here is a table that compares the two names. [7]
| Formula | Common Name | Systematic Name |
|---|---|---|
| H2O | Water | Dihydrogen monoxide |
| NH3 | Ammonia | Nitrogen trihydride |
| CH4 | Methane | Carbon tetrahydride |
| PH3 | Phosphine | Phosphorus trihydride |
| SiH4 | Silane | Silicon tetrahydride |
| BH3 | Borane | Boron trihydride |
| B2H6 | Diborane | Diboron hexahydride |
Learning how to name covalent compounds helps students understand chemical formulas and communicate clearly in science. By using the IUPAC naming rules, you can confidently identify, describe, and work with different compounds in the classroom and beyond.
