Chemistry: Rules for Naming Compounds, Polyatomic Ions

Is there a metal present?

NO: This is type III, use prefixes (ex: Dioxygen difluoride)

YES: Then, does the metal form more than one cation?
If so, Type II: determine the charge of the cation and use a Roman numeral after the element name for the cation
If no, it is Type I. Use the element name for the cation.

1. Cation always named first and the anion is named second.
2. A monatomic cation takes its name from the name of the element. For example, Na+ is called sodium in the names of compounds containing this ion.
3. A monatomic anion is named by taking the root of the element name and adding -ide. (ex: Cl- ion is called chloride)

Using the principle of charge balance, determine the cation charge.
Include in the cation name a Roman numeral indicating the charge.

Both type 1 and type 2 binary ionic compounds can involve polyatomic ions that must be memorized

Note on several series of polyatomic anions that contain an atom of a given element and different numbers of oxygen atoms: these anions are called OXYANIONS

When there are two members in a series like this, the name of the one with the smaller # of oxygen atoms ends in -ite and the name of the one with the larger # ends in -ate.

ex: sulfite SO3 2- and sulfate SO4 2-

When more than two oxyanions make up a series, hypo- (less than) and per- (more than) are used as prefixes to name the members of the series w/the fewest and the most oxygen atoms

ex: CLO – (hypochlorite)
CLO2 – (chlorite)
CLO3 – (chlorate)
CLO4 – (perchlorate)

can think of -ite being the suffix for the “sprite,” or the oxyanion with the smaller number of oxygen atoms

Binary covalent compounds are formed between two nonmetals. Although these compounds do not contain ions, they are named very similarly to binary ionic compounds:

1. The first element in the formula is named first, using the full element name.
2. The second element is named as if it were an anion
3. Prefixes are used to denote # of atoms present
4. Prefix mono- is never used for naming the first element. Ex: CO is called carbon monoxide, not monocarbon monoxide.

An acid can be viewed as a molecule with one or more H+ ions attached to an anion. (So, yes: HCL is an acid)

If the anion does not contain oxygen, the acid is named with the prefix hydro- and the suffix -ic.
example: HCL is hydrochloric acid

When the anion contains oxygen, the acidic name is formed from the root name of the anion with a suffix of -ic or -ous depending on the name of the anion.

1. If the anion name ends in -ate, the suffix -ic is added to the root name. ex: H2SO4 contains the sulfate anion (SO4 2-) and is called sulfuric acid.

2. If the anion name ends in -ite, the -ite is replaced by -ous. Ex: H2SO3 (contains sulfite -> SO3 2-), is named sulfurous acid

So basically, when naming acids and there is oxygen in the anion, use -ous if the anion name ends in -ite and -ic if the anion name ends in -ate.