Naming Compounds Notes
Remember the components of an ionic compound: metal + non-metal
Remember the components of a covalent compound: non-metal + non-metal
Naming Compounds
Rather than calling things just by familiar names, the IUPAC (International Union of Pure
and Applied Chemistry) has developed a system of rules for naming compounds.
Examples:
“Milk of magnesia” is called magnesium hydroxide - Mg(OH)2
“soda ash” is called sodium carbonate - Na2CO3
Binary means two different elements
In a binary compound, the least electronegative element is written first.
Binary compounds, like most compounds, will have a first name and a second name.
Naming Binary Covalent Compounds
Except for when naming an acid, the first name is simply the name of the first element listed
in the formula. The second name is the name of the second element listed with “ide”
replacing the ending. Also, in a binary compound, prefixes are used to tell how many of each
compound is present.
1 = mono
2=di
3=tri
4=tetra
5=penta
6=hexa
Examples:
PCl3 = phosphorus trichloride
CO = carbon monoxide
CO2= carbon dioxide
SF6= sulfur hexafluoride
Naming Binary Ionic Compounds
Binary = two different elements
Covalent = metal + non-metal
The only difference from binary covalent compounds is DON’T USE PREFIXES.
Examples:
NaCl= sodium chloride
K2S= Potassium sulfide
MgH2= Magnesium Hydride
Binary Ionic Compounds with Transition Metals
If the binary ionic compound contains a transition metal, Roman numerals are used to
denote the oxidation number of the metal. This is called the “Stock system.”
Examples:
FeCl2= Iron(II) Chloride
FeCl3= Iron (III) Chloride
SnO= Tin(I) Oxide
SnO2= Tin(II) Oxide
(Hint: use the criss-cross method in reverse to figure these out!)
Polyatomic Ionic Compounds
Polyatomic = two or more different elements
Ion = charged
Polyatomic ion = a charged compound
With only 2 exceptions, all polyatomic ions are anions (negatively charged ions).
Polyatomic anions that contain oxygen and one other element are called oxyanions.
Other Common Polyatomic Ions
Hydroxide = OHAmmonium = NH4+
Bicarbonate = HCO3Acetate = C2H3O2Naming Compounds with Polyatomic Ions
Naming compounds that contain polyatomic ions is really easy! The first name is the first
element listed (the cation) and the second name is the name of the polyatomic ion.
**Exception: when naming a compound that includes NH4+, it will be the first name;
second name will be the element name with “ide” ending.
Naming Hydrates
A hydrate is a compound that holds a specific amount of water within its crystalline
structure.
A hydrate’s formula is written this way:
Na2CO3•H2O= sodium carbonate monohydrate
To name a hydrate, name it just as you would a polyatomic ion compound, then add
“hydrate” with the appropriate prefix.
Examples:
CuSO4•5H2O= copper sulfate pentahydrate
CoCl2•6H2O= colbalt chloride hexahydrate
SnCl2•2H2O = tin chloride dihydrate
Binary Acids
A binary (two element) acid is a covalent compound that begins with hydrogen and includes
one other non-metal. Example: HCl
When a covalent compound like HCl is dissolved in water, it forms an acid called
hydrochloric acid.
Binary acids usually include hydrogen + a halogen, but there are some exceptions.
Examples of binary acids are:
HF, HCl, HBr, HI, and H2S
The number of H’s present in the formula depends on what the partner element is.
Binary acids are named by the following steps:
-Name begins with “hydro” (refers to hydrogen)
-Name includes the root of the other non-metal
-Name ends with “ic” and the word “acid”
Examples:
HBr- hydrobromic acid
H2S- hydrosulfuric acid
HF- hydrofluoric acid
Ternary Acids
A ternary acid contains three elements
Hydrogen
Oxygen
One other non-metal
The names of ternary acids come from the hydrogen plus the oxyanion within the formula.
If the anion’s name ends in “ate,” then the ending changes to “ic” and the word acid is
added.
Example:
ClO3- = chlorate
NO3- = nitrate
SO42- = sulfate
HClO3 - chloric acid
HNO3 - nitric acid
H2SO4 - sulfuric acid