Tutorials

Naming Covalent Compounds

Core Concepts

In this tutorial, you will learn how to derive the name of covalent compounds from the molecular formula.

Topics covered in other articles

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 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.

  1. The first element will be the most electropositive of the two. For more information on the periodic trend of electronegativity, click here.
  2. 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 say we have 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 atomsPrefix
1mono
2di
3tri
4tetra
5penta
6hexa
7hepta
8octa
9nona
10deca

Examples:

  1. What is the name of the diatomic compound Li2?
    • dilithium
  2. What is the name of the binary compound NO?
    • nitrogen monoxide
  3. 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!

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