Naming Covalent Compounds — Rules & Examples

Naming Covalent Compounds

How to name covalent compounds:

1. Order the elements correctly. The element more to the left or bottom of the periodic table is listed first. It's followed by the element more to the right or on the top of the periodic table. That's the more electronegative element.

• There is an exception you should know. If a molecule contains oxygen and a halogen, the halogen is listed first followed by oxygen. In this case, the halogen is an exception to the octet rule.

1. Use prefixes to note the number of each specific atom in a molecule. Typically, if the first element is singular, then the prefix "mono" is not needed.

2. Name the first element by its regular name and name the second element by its "root" followed by "ide (Ex: Oxide or Nitride).

Naming Covalent Compounds Walkthrough:

Name the following covalent compound: $N_{2}O_{3}$

1) Figure out the order. In this case, nitrogen is more to the left on the periodic table than oxygen. So, nitrogen will be named first followed by oxygen

Nitrogen Oxygen

2) Change the second element so that it only has its root name followed by ide.

Nitrogen Oxide

3) Add prefixes to each element (prefixes note the number of each element in the molecule).

Dinitrogen Trioxide

Naming Covalent Compounds Cheat Sheet

Converting Names to Molecular Formulas

We can also determine the molecular formula from the name.

1. Use the names to determine the atomic symbols of the elements.

2. Use the prefixes to determine the mole ratios.

For example, let's consider boron trihydride.

1. The name tells us to write the atomic symbols for boron and hydrogen. So, BH.

2. Boron doesn't have a prefix so it remains as is.

3. Hydrogen has a "tri-" prefix. So, there are three hydrogens. So, our molecular formula is $BH_{3}$.

Other Naming Schemes to Study

There are some other naming schemes you'll encounter as well. Here are some of the other explanations we have!

• Naming Ionic Compounds

• Oxoanions

• Polyatomic ions

• Naming Acids and bases

Other branches of chemistry like organic and inorganic chemistry have their own unique naming systems. But, these lessons will get you through all of general chemistry.

(Video) How To Name Covalent Molecular Compounds - The Easy Way!

By The Organic Chemistry Tutor

It is important to make sure you can identify a covalent compound over an ionic compound because they have different naming rules. First, $MgCl_2$ or magnesium chloride is compared to $SCl_2$ or sulfur dichloride. Magnesium chloride is ionic whereas sulfur dichloride is molecular. Molecular compounds require the use of prefixes to indicate the number of atoms of the elements.

Molecular and ionic compounds are distinguished from each other easily by thinking about the charges associated with the atoms. Ionic compounds are made of ions with ionic charges. The electrostatic interactions hold the ions together. Another way to tell if a compound is ionic is if it is made of a metal and a nonmetal. Two nonmetals create a molecular compound.

The prefixes used are: mono = 1 di = 2 tri = 3 tetra = 4 penta = 5 hexa = 6 hepta = 7 octa = 8 nona = 9 deca = 10

Examples are: $CO$ vs $CO_2$ If there is no subscript assume it is 1. When the first element has a subscript of 1, the prefix is not needed. So, $CO$ is carbon monoxide meaning one carbon and one oxygen. $CO_2$ is carbon dioxide meaning one carbon and two oxygens.

$N_2O_5$ vs $NO_2$ Dinitrogen pentoxide and nitrogen dioxide. Notice that these both end in -ide

$NO$ vs $N_2O_3$ Nitrogen monoxide and dinitrogen trioxide

The video concludes with various examples, try them on your own!