C06 Nomenclature
February 12, 2013
NOMENCLATURE ­ a systematic way of naming chemical compounds
So far, we have looked at two types of compounds ­ ________________ and _________________. Ionic compounds are formed when oppositely ______________ ions stick or bond together. There are two reasons why this happens:
1. Atoms lose or gain electrons to fill their ___________ __________.
2. Oppositely charged ions stick together to form an ________ compound.
The simplest ionic compounds result when a group 1 element bonds with a group _____ element.
ex. Sodium chloride
OR a group 2 element bonds with a group ______ element.
ex. Magnesium oxide
More complex ionic compounds can be formed when the charges of the cation and _________ are not equal such as aluminum oxide.
Molecular compounds are different because the atoms ______ their valence ________ instead of becoming ions. The properties of ionic compounds are vastly different then molecular compounds (salt vs. Lauric acid). Another difference between ionic compounds and molecular compounds is that ionic compounds occur in fixed ratios for any two elements. CaCl2, NaCl, Al 2O3
However, a varied of ratios can exist for molecular compounds.
CH4 & C2H6 or CO & CO 2
As a result, chemists have created their own naming system (nomenclature) to help distinguish between the various types of compounds. 1
C06 Nomenclature
February 12, 2013
NAMING IONIC COMPOUNDS
Ionic compounds are formed when a metal bonds to an oppositely charged ___________________. There are 3 categories for ionic compounds because of the various types of ionic compounds.
Category 1 ­ Simple Ionic Compounds
• Elements which form ions with only 1 possible charge (simple metals & non­
metals.
Ex. Because the charge is known, chemists do not require this information in the name or formula.
Name ­ change the ending of the non­metal to "ide" ­ ignore everything else.
Formula ­ look up the charge and determine the ratio.
• Cross­over method can be used as a short­cut to determine the correct ratio.
Examples
1. sodium chloride ________ 2. K2O _______________________
3. magnesium phosphide ________ 4. AlCl3 _______________________
Complete the follong naming simple ionic compounds for homework
a. Magnesium oxide _____________
a. Li2O _________________________________
b. Aluminum nitride _____________
b. AlCl3 _________________________________
c. Potassium sulfide _____________
c. MgS _________________________________
d. Calcium bromide _____________
d. CaF2 _________________________________
e. Aluminum sulfide _____________
e. Al2O3 _________________________________
f. Beryllium oxide _____________
f. BeF2 _________________________________
g. Strontium phosphide _____________
g. K3P _________________________________
h. Sodium fluoride _____________
h. Mg3P2 _________________________________
i. Lithium selenide _____________
i. CaO _________________________________
j. Barium oxide _____________
j. Ag2S _________________________________
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C06 Nomenclature
February 12, 2013
Two more difficult categories of Ionic Compounds
Category 2 ­ Polyatomic ions
The prefix poly means _______ the suffix atomic means different ________, the word ion means ___________________so the term polyatomic ions refers to a group of atoms which form a single ion. These ions must be common enough to be given a common name so that chemists can easily identify ionic compounds from this group.
http://www2.pvc.maricopa.edu/tutor/chem/chem130/nomenclature/polyatomicion.html
NH4+ OH ­ ammonium hydroxide
HCO3­ hydrogen carbonate
CO32­ carbonate
NO3­ nitrate
PO4­3 phosphate
SO42­ sulfate
The difficulty with naming polyatomic ions is the ability to recognize the common ion. Once recognized, the same rules apply for naming ionic compounds
Name ­ change the ending of the non­metal to "ide" ­ ignore everything else unless the non­metal is a polyatomic.
Formula ­ look up the charge and determine the ratio
∙ Cross­over method can be used as a short­cut to determine the correct ratio
• A bracket might have to be used around the polyatomic
Examples
1. sodium hydroxide __________
2. Li2 CO3 ______________________
3. magnesium phosphate ________ 3. Al2 (SO4 )3 _______________________
Complete the following naming polyatomic ionic compounds for homework
a. magnesium carbonate ________________
a. Li2SO4 ___________________________
b. aluminum nitrate __________________
b. MgSO4 ____________________________
c. potassium sulfate __________________
c. K2CO3 ____________________________
e. aluminum sulfate__________________ d. Na2SO4 ___________________________
f. sodium carbonate __________________
e. K3PO4 ____________________________
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C06 Nomenclature
February 12, 2013
Category 3 ­ The Transition Metals
Of the ionic compounds we have looked at so far, the charge of both ions is fixed and so only one possible ratio can exist when the compound is formed. Chemists found that some elements formed ionic compounds in different ratios. And so, they had to come up with a different system when naming these ionic compounds (of the 2 possible strategies, we will look at only the stock system).
The key to the naming of these ionic compounds is the inclusion of the charge for the element that is found with multiple charges.
Ex. iron (II) oxide & iron (III) oxide
The charge of the iron in iron (II) oxide would be _____
The charge of the iron in iron (III) oxide would be _____
Look on your periodic table and list other elements that can have multiple charges.
When given the formula, the charge of the unknown ion is to be deduced from the formula. This is likely the most difficult of all nomenclature scenarios.
Ex. FeO ________________ and Fe2 O3 ___________________
Try the following questions for homework.
a. tin (II) fluoride _________________
a. PbS _____________________________
b. lead (IV) nitride _________________
b. SnO2 _____________________________
c. iron (III) chloride _________________
c. NiO _____________________________
d. copper (I) oxide _________________
d. CuI2 _____________________________
SUMMARY
Ionic Compounds ­ start with a _________, can be divided into 3 categories:
1. Simple ionic compounds where the charges are known and it is easy to determine the correct ratio.
ex.
2. Polyatomic ionic compounds where students must recognize a small list of known groups of atoms which form a single ion.
ex.
3. Transition metals where the ions formed can vary and therefore the name must indicate the specific ion in the compound.
ex.
Molecular compounds ­ have completely different properties from ionic compounds and they can exist in different ratios. Therefore, a completely different naming system was established.
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C06 Nomenclature
February 12, 2013
MOLECULAR COMPOUNDS
Molecular Compounds are formed with non ­ ____________ or elements found on the ___________ hand side of the periodic table. Prefixes are used to indicate the specific ratio for that compound.
Rules
1. The more positive atom is written first (the atom which is the furthest to the left and to the bottom of the periodic table)
2. The more negative second atom has an "­ide" ending.
3. Each prefix indicates the number of each atom present in the compound.
4. If there is only one atom of the first element, we don't use any prefix.
Prefixes
Number Prefix of Atoms 1
2
3
4
mono
5 penta
di
tri
tetra
Number of Atoms
6
7 8 9 10 Prefix hexa
hepta
octa
nona
deca
Examples. 1. tetraphosphorus decasulfide ___________________
2. CO
________________________________
3. CH4 ________________________________
4. dicarbon hexahydride
__________________
Complete the following naming molecular compounds for homework
a. carbon dioxide _______________
a. CF4 ______________________________
b. silicon dioxide _______________
b. NF3 ______________________________
c. dinitrogen monoxide _______________
c. NH3 ______________________________
d. diphosphorus trisulphide _______________
d. P 2S5 _____________________________
e. dichlorine monoxide _______________
e. PBr3 ______________________________
f. carbon disulphide _______________
f. PF5 ______________________________
g. bromine gas _______________
g. ICl _____________________________
h. sulphur trioxide _______________ h. CS2 ______________________________
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