1. Covalent Nomenclature

2. Steps for Naming Covalent Compounds
Number of Atoms
Prefix 1
mono- 2
di- 3
tri- 4
tetra- 5
penta- 6
hexa- 7
hepta- 8
octa- 9
nona- 10
deca-
Write the names of the elements in the same order that they appear in the formula.
Change the ending of the last element to “-ide” (just like in ionic names).
Add a prefix for each element telling how many atoms of that element appear in the formula.
Exception: If there is only one of the first element in the name, you don’t have to write “Mono-” in front of it. Think of Carbon Dioxide as an example.

3. Example 1 What is the name of the compound whose formula is BCl3?
1. Write the names of the elements in the same order that they appear in the formula.
Boron Chlorine
2. Change the ending of the last element to “-ide” (just like in ionic names).
Boron Chloride
3. Add a prefix for each element telling how many atoms of that element appear in the formula.
Boron Trichloride

4. Example 1
Notice that I did not write “Mono-” in front of Boron because it is the first element in the name.
Boron Trichloride

5. Dinitrogen Tetrahydride
Example 2
What is the name of the compound whose formula is N2H4?
1. Write the names of the elements in the same order that they appear in the formula.
Nitrogen Hydrogen
2. Change the ending of the last element to “-ide” (just like in ionic names).
Nitrogen Hydride
3. Add a prefix for each element telling how many atoms of that element appear in the formula.
Dinitrogen Tetrahydride

6. Dinitrogen Tetrahydride
Example 2
Notice that I wrote “Di-” in front of Nitrogen. Even though it was the first element in the name, it had a prefix other than “Mono-”, so we had to write the prefix.
Dinitrogen Tetrahydride

7. Name → Formula
You will sometimes need to write the formula for a compound when given the name. This is easy, since you already have the elements in order and have been told how many atoms of each element there are.
Dinitrogen Monoxide
N2O

8. Exceptions You Need to Memorize: Acids
You are expected to know the formulas/names of the following compounds. They are a special class of covalent compounds called acids, which we will learn more about later. Here is what you need to know for now. I’ve listed them from most common (top) to least common (bottom).
Name
Formula
Hydrochloric Acid
HCl
Sulfuric Acid
H2SO4
Acetic Acid
C2H4O2
Nitric Acid
HNO3
Citric Acid
C6H8O7

9. Exceptions You Need to Memorize: Diatomics
Diatomics means two atoms. There are seven elements on the periodic table that appear as covalently bonded diatomics. They begin with Nitrogen (atomic number 7), and make the shape of a 7 on the periodic table.
Name
Formula
Molecular Nitrogen N2
Molecular Oxygen O2
Molecular Fluorine F2
Molecular Chlorine
Cl2
Molecular Bromine
Br2
Molecular Iodine I2
Molecular Hydrogen H2