Scientific Tutor

What sections should I know before attempting to learn this section?

—> Covalent, Ionic, and Metallic Bonds

 

How do you name covalent (molecular) compounds?

For the covalent system of naming, it depends on how many of each element there is in a compound. You describe the amount of each element by using a prefix word that indicates a number. The prefixes names for the system are as follows:

 

 

These prefixes are used in front of each elemental name in a compound. Sometimes the “a” on the end of the prefixes, like penta or octa, will be omitted. Don’t worry about it too much, right now.

 

Examples: Give the name of each compound using the covalent prefixes and a regular periodic table. VIDEO Covalent Naming Examples 1.

C2O4	Dicarbon Tetroxide
P3Br10	Triphosphorus Decabromide

 

One trick in this whole system has to do with the mono- prefix. Mono- is a special prefix that you do not always use. You have heard this exception before but may not have realized it. Take the compound CO₂. Think… what is the name of it? Right, carbon dioxide. So why does carbon not have a mono- prefix on it? The exception I was talking about earlier is just that. If the first element in the compound is only one of that element, you do not use the mono- prefix. Here’s an additional example to drive the point home. Another common compound you have heard of is carbon monoxide. So what does it look like? That is right: CO. It is a perfect example of how the first element, carbon, has no prefix, but the second has a prefix. This rule is only true for the mono- prefix, so do not use it for any other purposes in covalent naming.

 

VIDEO Covalent (Molecular) Naming Demonstrated Example 1: Give the name of each compound using a regular periodic table and the covalent prefixes.

 

ClF₂

 

Step 1:

What does Cl stand for?

Answer: Chlorine

 

Step 2:

How much chlorine do you have?

Answer: 1

 

Step 3:

What is the prefix for the chlorine?

Answer: It should be mono but since it is the first element you don’t write it.

 

Step 4:

What does F stand for?

Answer: Fluorine

 

Step 5:

How much fluorine do you have?

Answer: 2

 

Step 6:

What is the prefix for the fluorine?

Answer: Di

 

Step 7:

How do you modify the ending of fluorine?

Answer: Becomes fluoride

 

Step 8:

What is the complete chemical name?

COMPLETE ANSWER: Chlorine Difluoride

 

PRACTICE PROBLEMS: Give the name of each compound using a regular periodic table and the covalent prefixes.

O2F2	Dioxygen Difluoride
PCl3	Phosphorous Trichloride
N4S5	Tetranitrogen Pentasulfide
Se7I10	Heptaselenium Deciodide
H2O	Dihydrogen Monoxide
BBr3	Boron Tribromide