Grade 11 Chemistry
Nomenclature
A system exists that is used to name chemical compounds. The chemical formula gives
the following information:
1)
2) covalent:
ionic
1) Binary Compounds:
A binary compound is one that contains only two kinds of elements. If it is ionic, the
first element is a __________and the second is a_______________.
Formula to Name
To write the name of a binary compound if given the formula, one simply writes the
name of the metal first, followed by the name of the non-metal, with its ending changed
to –IDE.
Example:
NaCl __________________
Al2O3 ___________________
Ag2S ____________________
Na3P ____________________
Name to Formula
Finding the formula when given the name of a binary compound is a little more
complicated. It is important that you include the appropriate subscripts when writing the
formula. This shows you how many of each atom is included in the substance.
Example: NO2 has ______ atoms of N and ______ atoms of O
H3(PO)4 has ______ atoms of H, ______ atoms of P and ______ atoms of O
Mg(NO3)2 has _____ atoms of Mg, _____ atoms of N and _____ atoms of O
Use the following steps when writing a formula:
1) Find the valence of both elements in the substance. Use the periodic table to help you.
2) Write the symbols for the two elements in the substance (remembering to write the
metal first and the non-metal last) and include the valences.
3) “Cross-over” the two valences and write them as subscripts for the other element.
4) For IONIC compounds, reduce the subscripts to their lowest ratio.
5) Do not show the subscript “1” in a formula – just leave it blank and the “1” is
assumed.
Example: aluminum sulfide
aluminum nitride
aluminum fluoride
2) Elemental Substances
Elements exist either as individual atoms or as covalent molecules.
Metals and noble gases tend to exist as collections of single atoms that tend to stay
together. The formula for these elements is simply to write the element alone.
Non-metals tend to exist as covalent molecules. Their formulas can be determined by
drawing Lewis Structures.
Example:
sodium _________ copper _________
aluminum _________
hydrogen ________ nitrogen __________ fluoride ____________
sulfur ________
phosphorus ________
3) Common Names
Some compounds will always be known by their common names, even though there is a
more “scientific” name for them.
Example:
H2O ______________________
O3 _______________________
NH3 ________________________
CH4 ________________________
4) Compounds Containing Metals with Variable Valences
Some metals can have different valences depending on what molecule they are in. In
order to be able to name these molecules, it is important to memorize the variable
valences of these elements.
gold:
cobalt:
copper:
iron:
mercury:
tin:
lead
aurous Au+1
cobaltous Co+2
cuprous Cu+1
ferrous Fe+2
mercurous Hg+1
stannous Sn+2
plumbous Pb+2
auric Au+2
cobaltic Co+3
cupric Cu +2
ferric Fe+3
mercuric Hg+2
stannic Sn+4
plumbic Pb+4
There are two methods of naming compounds when the metallic element can have a
variable valency:
Suffix Method:
This method is not used much anymore since it involves more memorization, but you still
see old bottles of chemicals that are named this way, so it is important to be familiar with
the method.
To name the substance, you use the suffix “ous” when the lower valency exists, and you
use the suffix “ic” when the higher valency exists.
Example: FeS _________________________
HgBr ________________________
Co2O3 ________________________
cuprous oxide ____________
plumbous chloride ___________
auric iodide ___________
Stock Method:
This method is easier because the valence of the metal is written in Roman numerals
between the two elements.
Example:
lead (II) oxide ___________
Cu2O ________________________
copper (II) bromide __________
SnH4 ________________________
manganese (IV) oxide __________ FeO _________________________
5) Compounds Containing Two Non-Metals: The Prefix System
If a binary compound is composed of two non-metals (ie. a covalent compound), the
subscript on each element is simply tranformed into a prefix that precedes the name of
each element. The second element still has its ending changed to –IDE.
NOTE: If the prefix of the first element is “mono”, it is NOT used.
Example:
As2S3 ______________________ NO2 _________________________
N2O5 _______________________ CCl4 ________________________
The prefixes used are: 1 – mono, 2 – di, 3 – tri, 4 – tetra, 5 – penta, 6 – hexa, 7 – hepta,
8 – octa, 9 – nona, 10 – deca
6) Binary Acids
If a binary compound follows the formula: hydrogen + group 16 or 17 atom, it
becomes a binary acid when dissolved in water. The subscript (aq) is used to show that
the substance is dissolved in water.
Example:
HF ________________________
HCl _______________________
H2S ________________________
HF(aq) _______________________
HCl(aq) ______________________
H2S(aq) ______________________
7) Polyatomic Ions
A polyatomic ion is a group of atoms that are covalently bonded together and that have a
charge. It is necessary to memorize the following polyatomic ions (the more common
ones are in bold):
CN-1 cyanide
OH-1 hydroxide
C2H3O2-1 acetate
ClO3-1 chlorate
MnO3-1 manganate
NO3-1 nitrate
OCN-1 cyanate
SCN-1 thiocyanate
CO3-2 carbonate
C2O4-2 oxalate
CrO4-2 chromate
Cr2O7-2 dichromate
O2-2 peroxide
SO4-2 sulfate
S2O3-2 thiosulfate
AsO4-3 arsenate
PO4-3 phosphate
NH4+1
ammonium
Often polyatomic ions will have different numbers of oxygen atoms in the group of
atoms. When this occurs, the charge on the ion STAYS THE SAME!!!
Example: using chlorate, ClO3-1
Two Less Oxygens
ClO-1
One Less Oxygen
ClO2-1
Stable Polyatomic Ion
ClO3-1
One More Oxygen
ClO4-1
Example:
HYPOstemITE
stemITE
stemATE
PERstemATE
“hypochlorite”
“chlorite”
“chlorate”
“perchlorate”
MnO4-1 ________________________
NO2-1 _________________________
SO2-2 _________________________
CrO4-2 ________________________
PO5-3 _________________________
8) Polyatomic Salts
These compounds are formed when metals combine with polyatomic ions.
Formula to Name:
1) Write the full name of the metal first. If the metal is a transition metal, it will be
necessary to use the Stock system or the Suffix system to indicate its valence.
2) Identify the polyatomic ion, and remember its stable form, name and charge. Then
notice if it has more or less oxygens than usual, and alter it appropriately.
Example:
CaSO4 ____________________________________
Fe(NO3)2 ____________________________________
Sn3(PO2)4 _____________________________________
Na(ClO4) ____________________________________
Name to Formula:
1) Identify the polyatomic ion and remember its usual formula and charge.
2) Decide whether there are more or less oxygens than usual in the formula. If there are,
alter it appropriately by adding or removing oxygens WITHOUT changing the charge.
3) Decide on the charge on the positive metal, remembering that the entire substance
must have a total charge of zero.
4) Use the cross-over rule to find the proper subscripts, and reduce.
Example:
sodium hydroxide ____________
ferric hypophosphite ______________
gold (I) oxalite ______________
mercurous persulfate ___________________
magnesium cyanide __________________
9) Polyatomic Acids
If a substance follows the formula: hydrogen + polyatomic ion, it becomes a
polyatomic acid when it is dissolved in water. Once again, the subscript (aq) is used to
show that the substance is dissolved in water.
The system of naming polyatomic acids is more complex than binary acids. Basically,
you must remove the “hydrogen” and then change all –ATE endings to –IC ACID and all
–ITE endings to –OUS ACID.
Example:
H2SO4
H2SO5
H2SO3
H2SO2
hydrogen sulfate
hydrogen persulfate
hydrogen sulfite
hydrogen hyposulfite
H2SO4(aq)
H2SO5(aq)
H2SO3(aq)
H2SO2(aq)
sulfuric acid
persulfuric acid
sulfurous acid
hyposulfurous acid
Example:
H2CO3 _________________________________________
H3PO4(aq) _________________________________________
H3PO2(aq) _________________________________________
HMnO2 _________________________________________
H2CrO5(aq) ___________________________________________
Example:
hydrogen percarbonate _____________________
percarbonic acid ________________________
hydrogen arsenite ____________________________
arsenous acid __________________________
10) Polyatomic Acid Salts
If a substance follows the formula: metal + hydrogen + polyatomic ion, it is a
polyatomic acid salt.
Formula to Name:
1) Write down the name of the metal. If it has a variable valency, use the Stock system
or the Suffix system to indicate which valence is used here.
2) Identify the polyatomic ion. Write the appropriate suffixes and prefixes according to
the number of oxygens in the polyatomic ion.
3) Between the name of the metal and the polyatomic ion, write the word “hydrogen” or
the word “bi” to represent the hydrogen.
Example:
NaHCO3 ______________________________________
Li2HPO3 ______________________________________
HgHSO4 _______________________________________
Name to Formula:
1) Write down the formula of the metal, and its valence.
2) Find the polyatomic ion and its charge. Remember to change the number of oxygens
according to the suffixes and prefixes in the name.
3) Add a hydrogen to the polyatomic ion, thus reducing its negative charge by one.
4) Use the cross-over rule to determine the subscripts of the formulas – remember that the
hydrogen stays with the polyatomic ion.
Example:
magnesium bioxalate ________________________
copper (I) hydrogen arsenite ______________________
calcium bicarbonate ________________________