CHM101 Compound Naming

COMPOUNDS: Names and FormulasObjectives
1. Distinguish between the common and systematic names for given substances.
2. Describe the meaning of the classification system of binary, tertiary, and quaternary
compounds.
3. Know and use the nomenclature rules for naming compounds from a given formula for:
a. ionic compounds that are
(i) binary with fixed charge (type I) metals
(ii) binary with variable charge (type II) metals
(iii) tertiary or quaternary
(iv) binary or oxy acids
b. binary molecular compounds.
4. List the names, charge value and symbol of each of the polyatomics, and write the formulas
of compounds which contain polyatomic ions when given the name and vice-versa.
Introduction
Chemical NOMENCLATURE names compounds systematically. Common names do
not translate well into other languages and not every chemist speaks English. However, all
chemists understand systematic names because they are based on the chemical composition of
the compound and follow the rules for naming devised by the International Union of Pure and
Applied Chemistry (IUPAC).
Atomic elements exist as single atoms. Molecular elements exist as diatomic molecules
(H2, N2, O2, F2, Cl2, Br2, or I2) or larger molecules (P4, S8 or C as a “Bucky Ball”). All molecular
elements are made of nonmetals bonded to themselves.
Compounds consist of two or more DIFFERENT elements chemically combined.
Molecular compounds are either organic or inorganic types and consist of two or more nonmetals
or a metalloid and a nonmetal. Ionic compounds have a metal and one or more nonmetals in their
makeup.
Table Salt
Carbon “Bucky Ball”
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In chemical nomenclature, compounds are classed by bond type, origin and their number
of different elements. Bonds are either ionic or covalent. By origin, they derive from either a
living source (organic) or nonliving source (inorganic). Carbon monoxide and carbon dioxide,
although produced by living organisms, are classified as inorganic molecules because they are
primarily made by nonliving processes like combustion.
Binary compounds only have two different elements like NaCl and H2O. Tertiary
compounds have three different elements such as HNO3 and CaCO3. Quaternary compounds
have four or more different elements, e.g., NaHCO3 and (NH4)2SO4.
Chemical formulas are a chemist’s shorthand for identifying compounds and it provides
the elements and their relative numbers in the compound’s makeup. Each element is represented
by its symbol: Na for sodium, C for carbon or O for oxygen. Subscripts on each symbol tell the
number of atoms or ions present; e.g., Sodium Carbonate has 2 sodium, 1 carbon and 3 oxygen
in its makeup and its formula is written as Na2CO3. Note that the number one is NOT written
since a symbol alone means you have at least one atom or ion of that element.
Ion Formation
Ionic compounds are formed by the combination of positive and negative ions. Ions are
charged atoms formed when one or more electrons are gained or lost.
Cations are positive ions. They are formed by the loss of electrons. Metals lose electrons
to be stable because the ion they form has the same electron configuration as a noble gas. Cations
are smaller in size than their original atom.
potassium
potassium ion
+
K→K +e
–
Cations are named just as the original atom with or without a charge representation. E.g.,
the sodium atom, Na°, forms the sodium ion, Na+, and the iron atom, Fe°, can form either an iron
(II), Fe2+, or an iron (III), Fe3+
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Nonmetals tend to gain electrons to become stable. Therefore, negative ions, called
anions, are larger than their atoms. In a binary compound with a metal, an anion name takes the
root of the nonmetals’s name and adds the suffix “ide.” E.g., chlorine, Cl°, becomes chloride, Cl, and oxygen, O°, becomes oxide, O2-.
chlorine
chloride ion
–
–
Cl + e → Cl
Writing Ionic Compound Names
To name a compound from its formula, you must first distinguish between ionic and
molecular formulas. A formula is ionic if it begins with the symbol of a metal or the symbol for
the ammonium ion, NH4+. Otherwise, it is molecular. Next, you need to determine if the metal
forms a fixed charge or a variable charge ion. Finally, is the anion a single nonmental or
polyatomic ion?
For Binary Ionic compounds with a fixed charge (type I), name the metal (cation) then
name the anion (nonmetal root + ide). E.g., AlF3 is aluminum for Al and fluoride for fluorine, F.
Ca3N2 is calcium nitride and KCl is potassium chloride. Note that ionic compounds do NOT tell
you how many of each element is present in the compound. This is because an ionic compound’s
formula is derived from balancing the charges on its ions.
For Binary Ionic compounds with a variable charge (type II), compound names follow
the same rule as fixed charge naming with the addition of the metal ion’s charge as a Roman
numeral in parentheses after the metal’s name. E.g., Fe2O3 is iron(III) oxide while FeO is iron(II)
oxide. Usually you can get the charge on the metal by using the subscript OR the charge on the
nonmetal ion.
Compounds with more than two different elements usually involve a polyatomic ion.
This is a group of elements that behaves as if it was a single ion. This is like a band that wins a
trophy at a competition; the trophy belongs to the band and not to any one member of the band.
Similarly, the charge on a polyatomic ion belongs to the entire group and not to any one element
in the group. With only two exceptions, NH4+ and H3O+, polyatomic ions are negatively charged.
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To name a compound with a polyatomic ion, name the cation as you would for a binary
compound and add the polyatomic ion’s name. E.g., Na2CO3 is sodium carbonate, Zn3(PO4)2 is
zinc phosphate and Pb(C2H3O2)2 is lead(II) acetate. Note that when more than one polyatomic
ion is needed in a formula it is first parenthesized and the subscript appears on the parenthesis.
Writing Ionic Formulas from Compound Names
To write an ionic formula, follow these rules:
1. Write the ion symbols with their charges next to each other.
•
•
•
Magnesium oxide
Lithium sulfate
Tin(IV) phosphate
𝑀𝑔2+ 𝑂2−
𝐿𝑖 +
𝑆𝑂42−
𝑆𝑛4+ 𝑃𝑂43−
2. Ask yourself this question: Are the charges equal in value but opposite in charge?
a. If YES, then write the symbols for the ions next to each other in cation anion order and
you have the formula.
•
Magnesium oxide
𝑀𝑔2+ 𝑂2−
becomes
MgO.
b. If NO, then “criss-cross” the charge numbers only. Use the charge number of each ion
as the subscript on the other ion.
•
•
Lithium sulfate
𝐿𝑖 +
𝑆𝑂42− becomes
Li2SO4.
Since you need more than one phosphate group, you must parenthesize the group before
you add the subscript.
Tin(IV) phosphate
𝑆𝑛4+ 𝑃𝑂43− becomes
Sn3(PO4)4.
3. CHECK: To be stable, an ionic compound must have a net charge of ZERO. Therefore, the
total positive charge must equal the total negative charge.
•
•
•
MgO:
Li2SO4:
Sn3(PO4)4:
1(+2) + 1(-2) = 0
2(+1) + 1(-2) = +2 + -2 = 0
3(+4) + 4(-3) = +12 + -12 = 0
Writing Molecular Compound Names
Molecular compounds bond by sharing their outermost electrons. Therefore, they are not
charged. To name these compounds, you must specify the number of atoms of each element
involved. This is done by adding a Greek prefix to each element’s name.
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These are the naming rules for all binary molecular
compounds.
# atoms
1
2
3
4
5
6
7
8
9
10
Prefix
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca
1. Name the first element; use a prefix if its subscript is
greater than one.
2. For the second element,
Prefix + root of name + ide.
E.g., CO2 is carbon dioxide, CO is carbon monoxide. Note
that when there is an “ao” or an “oo” combination between
the prefix and the root, you can drop the end of the prefix.
S2O4 is disulfur tetroxide. Note that molecular compound
subscripts may have a common multiple. This will be
important in writing their formulas from their names.
Writing Molecular Formulas from Compound Names
This is basically the reverse of naming these compounds. Use the names of the two
elements to get their symbols and add each element’s prefix as a subscript to its symbol.
Remember – if the first element has no prefix, it means there is only one atom in the compound
and the symbol always stands for “one of.”
E.g., Oxygen difluoride is OF2 and Disulfur monoxide is S2O.
Acids
Inorganic acids are hydrogen containing compounds in water solution and their formulas
begin with the symbol H. Acids come in two types: those formed from binary hydrogen
compounds and those formed from binary oxygen compounds.
If the original binary molecular compound is of the form “HxA”, then its name will be
Hydro + root of A’s name + ic acid
E.G.: HCl is named hydrochloric acid and H2S
is hydrosulfuric acid.
This group includes HF, HCl, HBr, HI, H2S, H2Se and HCN – an exception to the rule.
If the original compound is of the form “MOx”, then you have an “oxo-acid” former.
Oxo-acids are named based on the polyatomic ion it forms when ionized in water. The name has
the root of the polyatomic ion with either an “-ic” or an “-ous” suffix and the word acid.
NO2 + H2O → HNO3(aq) and this is named nitric acid from nitrate.
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NO + H2O → HNO2(aq) and this is named nitrous acid from nitrite.
Writing acid formulas from a given acid’s name requires that you pay attention to the
prefix and/or suffix used in the name. If the name begins with “hydro-“, you have a binary acid
and its formula will be HA or H2A depending on the charge on the element “A.” E.g.,
hydrochloric acid is HCl because A in this case is chloride with a charge of -1. For hydrotelluric
acid, the anion is telluride with a charge of -2 so its formula is H2Te.
For oxo-acids, there is no prefix and the formula will depend on the polyatomic ion in it.
If the suffix is “-ic”, then you have an “-ate” polyatomic ion. If it is “-ous”, you have an “-ite”
ion. Put this together with the named root and the polyatomic ion’s charge to write the formula.
E.g., chloric acid says it has a chlorate ion with a charge of -1 and its formula is HClO3.
Phosphorous acid says it has a phosphite ion with a charge of -3; its formula is H3PO3.
Prelaboratory Assignment
1. Classify each of the following compounds as ionic or molecular.
(a) Al2S3__________________
(b) NO2____________________
2. Classify each of the following metals as fixed charge or variable charge.
(a) Ba__________
(b) Cr__________
(c) Ni__________
(d) Mg__________
3. Name these ions – both cations and anions are given.
(a) Li1+_______________
(b) Br1-_______________
(c) Au3+_______________
(d) N3-_______________
(e) Sn2+_______________
(f) S2-_______________
4. In which of the following pairs of compounds are polyatomic ions present in BOTH.
(a) NO2 and KNO2
YES or NO
(c) NH4Br and KClO
YES or NO
(b) ZnSO4 and NH4Cl
YES or NO
5. In which of the following pairs of compounds would both names have a Greek prefix?
(a) NO2 and SO2
YES or NO
(c) OF2 and BaF2
YES or NO
(b) AlN and CO
YES or NO
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Fixed Charge (Type I) Cations and Anions (Group A elements):
For the A group metals, group number = charge.
To get the charge of a nonmetal, subtract 8 from the group number
Table below shows some examples
Cation
Name
Anion
+1
Li
lithium
F -1
+1
Na
sodium
Cl -1
Ga +3
gallium
Br -1
+2
Zn
Zinc
I -1
Name
fluoride
chloride
bromide
iodide
Variable-Charge (Type II) Metallic Cations
Cation
Cu +1
Cu +2
Fe +2
Fe +3
Sn +2
Sn +4
Pb +2
Pb +4
Au +1
Au +3
Hg +1
Hg +2
IUPAC Name
Copper (I)
Copper (II)
Iron (II)
Iron (III)
Tin (II)
Tin (IV)
Lead (II)
Lead (IV)
Gold (I)
Gold (III)
Mercury (I)
Mercury (II)
“Classical” Name
Cuprous
Cupric
Ferrous
Ferric
Stannous
Stannic
Plumbous
Plumbic
Aurous
Auric
Mercurous
Mercuric
Common Polyatomic Ions
Ion
NO3 -1
NO2 -1
NH4 +1
SO4 -2
SO3 -2
H3O +1
OH -1
O2 -2
PO4 -3
PO3 -3
Name
Nitrate
Nitrite
Ammonium
Sulfate
Sulfite
Hydronium
Hydroxide
Peroxide
Phosphate
phosphite
Ion
ClO4 -1
ClO3 -1
ClO2 -1
ClO -1
CO3 -2
HCO3 -1
C2H3O2 -1
CN -1
MnO4 -1
CrO4 -2
Cr2O7 -2
Name
Perchlorate
Chlorate
Chlorite
Hypochlorite
Carbonate
Bicarbonate
Acetate
Cyanide
Permanganate
Chromate
Dichromate
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Ionic Compound Names Exercise
Use the Cation and Anion Table provided to write the compound’s name. Rubric:
Step 1: Name the cation; it is the name for the metal element’s symbol.
If variable charge metal (type II/B block), add the charge as Roman numeral in ( ).
You can also do the classical name for the type II metals
Step 2: Name the anion from the symbol of the nonmetal element.
Take the root of the nonmetal’s name and add –ide OR name the
polyatomic ion.
Step 3: Put the two together as cation anion
.B = Binary, NB = Not Binary
Formula
1
Ca3(PO4)2
2
K2SO3
3
Mg(OH)2
4
CuBr2
5
Sn3(PO4)4
6
Ba(MnO4)2
7
AlCl3
8
AgNO3
9
FeCr2O7
10
Na2O
11
Au2O
12
Co3N2
13
SnO
14
NiI3
15
ZnO
16
PbSO4
17
Sn(CO3)2
18
Ni2(SO4)3
B/NB
Type 1/II Cation
Compound’s Name
19 Cr(C2H3O2)3
Mn(CN)3
20
21
HBr
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Ionic Compound Formulas Exercise
Use the Cation and Anion Table provided to write the compound’s formula. Rubric:
Step 1: Write the ion symbols with their charges next to each other.
Step 2: Ask yourself this question: Are the charges equal in value but opposite in charge?
a. If YES, then write the symbols for the ions next to each other in cation anion order and you
have the formula.
b. If NO, then “criss-cross” the charge numbers only. Use the charge number of each ion as
the subscript on the other ion.
Step 3: Reduce subscripts if necessary.
Step 4: The total positive charge plus the total negative charge must equal ZERO.
Compound’s Name
1
Binary Type I/II Cation
Anion
Compound Formula
Magnesium nitrate
2
Lithium iodate
3
Aluminum hydroxide
4
Zinc nitrite
5
Chromium(III) hypochlorite
6
Copper(I) sulfate
7
Ammonium phosphate
8
Lead(IV) oxide
9
Tin(IV) nitride
10
Manganese(II) sulfide
11
Ammonium acetate
12
Gold(I) nitrate
13
Manganese(III) hydroxide
14
Lead(II) phosphate
15
Copper(II) perchlorate
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Molecular Compound Names Exercise
Using the Greek prefixes and the rules, name these molecular compounds.
Formula
1
SO2
2
PCl5
3
N2O3
4
BF3
5
P4 O 6
6
SiO2
7
O2F2
8
AsCl3
9
SiSe
10
IF5
Compound’s Name
Molecular Compound Formulas Exercise
Using the Greek prefixes and the rules, write the formula for these molecular compounds.
Compound’s Name
1
Sulfur tetrabromide
2
Dinitrogen tetroxide
3
Phosphorus tribromide
4
Dihydrogen monoxide
5
Iodine monobromide
6
Nitrogen trichloride
7
Tetraphosphorus hexasulfide
8
Sulfur trioxide
9
Diboron trioxide
10
Arsenic trifluoride
Formula
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Name the Acid Exercise: Using the prefixes and/or suffixes, name these acids.
1
2
3
4
Formula
H2SO4
HCl (aq)
HBr(aq)
H3PO4
5
H2CO3
6
HClO
7
HC2H3O2
8
HBrO3
9
HClO4
10
11
12
H2SO3
H2Se(aq)
H3P(aq)
Binary/Oxyacid
Acid’s Name
Acid Formulas Exercise
Using the prefixes and/or suffixes, write the formula for these acids.
Treat acids as ionic compounds. All acids have hydrogen as their cation.
Step 1: Write the ion symbols with their charges next to each other.
Step 2: Ask yourself this question: Are the charges equal in value but opposite in charge?
a. If YES, then write the symbols for the ions next to each other in cation anion order and
you have the formula.
b. If NO, then “criss-cross” the charge numbers only. Use the charge number of each ion
as the subscript on the other ion.
Step 3: Reduce subscripts if necessary.
Step 4: The total positive charge plus the total negative charge must equal ZERO.
Acid’s Name
Binary/Oxyacid
Cation
Anion
Formula
Hydroiodic acid
Hydrocyanic acid
Perbromic acid
Nitrous acid
Phosphorous acid
Chromic acid
Hydrosulfuric acid
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Compound Lab
NAME_____________________________________________
SECTION #______________________
Postlaboratory Assignment
1. Which of these binary ionic compound names requires a Roman numeral?
(a) ZnO YES or NO
(b) Ag2S
YES or NO
(c) Cu2O
(d) FeBr3
YES or NO
YES or NO
2. What is the charge on the metal ion in each of these compounds?
(a) FeO _____
(b) NiCl2 _____
(c) Au2O3 _____
(d) Co3N2 _____
3. Name each of these ionic compounds.
(a) Cu2S _________________________
(b) AgCl _________________________
(c) ZnSO4 _________________________
(d) Na3N _________________________
(e) Ba(OH)2 _________________________ (f) CoO _________________________
4. Write the formulas for these ionic compounds.
(a) Iron (II) sulfide _______________
(b) Magnesium phosphate _______________
(c) Manganese (III) oxide _______________
(d) Ammonium sulfide _______________
5. Name each of these molecular compounds.
(a) S3F5 _________________________
(b) S4N2 _________________________
(c) CBr4 _________________________
(d) BrTe _________________________
6. Write the formulas for these molecular compounds.
(a) Iodine monochloride _______________ (b) Dinitrogen triiodide _______________
(c) Tetraphosphorus hexoxide _______________
7. Either name the acid from its formula or write the formula from the acid’s name.
(a) HClO3 ______________ (b) Sulfuric acid ___________ (c) hypobromous acid __________
(d) Carbonic acid _________ (e) HIO4 _______________
(g) HCN _________________________
(f) H2Te (aq) ____________________________
(h) hydroiodic acid ________________
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