Core Concepts
Naming covalent compounds and molecular compounds can be fun! In this tutorial, you will learn how to derive the name of covalent compounds, from the molecular formula. Molecular compound is just another name for a covalent compound, they mean the same thing.
Topics covered in other articles
- Naming ionic compounds
- IUPAC Naming of Organic Compounds
- Naming alkanes
- Ionic versus covalent bonds
- Constitutional Isomers
- What is Relative Configuration
Vocabulary
- Binary compound: Compound with two different elements.
- Diatomic compound: Compound that has two atoms that can either be different elements or the same element.
- Covalent compound: Molecules formed by covalent bonds in which electrons are shared between atoms.
What are covalent compounds?
A covalent compound, aka molecular compound, is a compound where two non-metals, or, a non-metal and a metalloid, are bonded together through the sharing of electrons.
How to name covalent compounds
[prefix–element] [prefix–element root–ide]
1. Choosing the first element for binary compounds
When deciding which element to place first, there are two things to remember.
- The first element will be the most electropositive of the two. For more information on the periodic trend of electronegativity, click here.
- If the molecular formula contains oxygen or a halogen (F, Cl, Br, I, At, Ts), then those elements will be placed first.
For example, if we had HCl, hydrogen would go first because it is more electropositive than chlorine.
2. Prefixes and suffixes
Let’s learn some chemistry prefixes. For example, say we have the pyrophoric gas diborane, B2H6. This tells us there are two boron atoms and 6 hydrogens. Below is a table of prefixes that relate the number of atoms present to the given prefix. Since boron has two, it will have the prefix “di”. Moreover, this means hydrogen will have the prefix “Hexa”. Note: only use the prefix “mono” in the second element. If there is only one atom of the first element, omit adding a prefix because we will just assume there is only one. Also, the prefix mono is usually paired with oxygen (dihydrogen monoxide).
Ultimately, we would end up with diboron hexahydride. Notice the last element has its root attached to “ide”. Remember to add this suffix to the last element.
| Number of atoms | Prefix |
| 1 | mono |
| 2 | di |
| 3 | tri |
| 4 | tetra |
| 5 | penta |
| 6 | hexa |
| 7 | hepta |
| 8 | octa |
| 9 | nona |
| 10 | deca |
For more help, please watch our lecture on naming inorganic compounds!
Examples:
- What is the name of the diatomic compound Li2?
- dilithium
- What is the name of the binary compound NO?
- nitrogen monoxide
- What is the name for the covalent compound HCl?
- hydrogen chloride
Note: you don’t have to capitalize the names.
If you enjoyed this article be sure to check out our other one on naming ionic compounds!