Practice with Names
Home Up Example: H and C Example: H and N Example: H and O Example: H and Cl Practice with Formulas Practice with Names Example: O and C Example: O and N Example: O and Cl Practice with Formulas and Names

 

Practice with Names

Prefix Names for Covalent Compounds

Let’s look at how to name the compounds we just worked with (from exercise 15).

CH4 can be named carbon tetrahydride to indicate that it contains one carbon atom and four hydrogen atoms bonded together. However, this compound was named long before its formula was figured out and it is called methane.

NH3 could have been named nitrogen trihydride to show that it contains nitrogen and three hydrogen atoms bonded together. This compound also was known and named long before its fomula was figured out. It is called ammonia.

H2O could have been called dihydrogen oxide or even dihydrogen monoxide to show that it contains two hydrogen atoms and one oxygen atom. But of course its common name as well as its chemical name is water.

The name for HCl is hydrogen chloride. Note that in this case there are no prefixes. When there is only one atom of an element in a molecule, the prefix mono- might or might not be used. Usually it is left off. When the elements can combine to form more than one compound and one of those compounds has just one atom of that element, the prefix mono- is generally used.
Formula Common Name Prefix Name
CH4 methane carbon tetrahydride
NH3 ammonia nitrogen trihydride
H2O water dihydrogen monoxide
HCl   hydrogen chloride

 

Practice

Now, name the compounds for which you determined the formulas (in exercise 15-e) using the prefix method. The correct answers follow.

 

Answers

The prefix name for SiH4 is silicon tetrahydride. Its common name is silane. The prefix name for PH3 is phosphorus trihydride. Its common name is phosphine. The proper prefix name for H2S dihydrogen sulfide. Since this is the simplest, most common, most expected and most reasonable of the sulfur-hydrogen compounds it is quite often simply called hydrogen sulfide. The lack of prefixes in this name leaves it to you (and your understanding of bonding and electron structure) to figure out that there are two hydrogens and one sulfur. HBr is called hydrogen bromide.

 

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