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ChemicalChemical NomenclatureNomenclature
Part IPart I
Rev. 032205Rev. 032205
Chemists need a Chemists need a systematic way systematic way
of naming of naming compoundscompounds
1. Prevent confusing one 1. Prevent confusing one compound for anothercompound for another
Consider these compounds:Consider these compounds:
FeO and FeFeO and Fe22OO33
Iron (II) oxide and iron (III) oxideIron (II) oxide and iron (III) oxide
COCO22 and CO and COcarbon dioxide and carbon monoxidecarbon dioxide and carbon monoxide
2. Formulas may be too 2. Formulas may be too complex to say.complex to say.
For carbon dioxide …For carbon dioxide …
… … you can easily say COyou can easily say CO22
But would you like to sayBut would you like to say
CC66HH44OCOCHOCOCH33COCO22HH
when you could say when you could say aspirinaspirinOr, evenOr, even acetylsalicylic acidacetylsalicylic acid
3. Families of compounds 3. Families of compounds have similarities in names have similarities in names
and propertiesand propertiesThe calcium carbonate in The calcium carbonate in
Tums is an antacid …Tums is an antacid …
… … any carbonate compound any carbonate compound will react with any acid.will react with any acid.
Chemical names …Chemical names … Prevent confusing one Prevent confusing one
compound for anothercompound for another Keep from having to say Keep from having to say
complex formulascomplex formulas Group compounds into Group compounds into
familiesfamilies
The convention for writing The convention for writing formulas of simple formulas of simple
inorganic compounds:inorganic compounds: The element with the The element with the
positive oxidation positive oxidation number is written first.number is written first.
A binary compound A binary compound contains only two contains only two kinds of elementskinds of elements
HH22O and HClO and HCl
COCO22 and N and N22OO55
NaCl and BiFNaCl and BiF33
Naming Binary Naming Binary Compounds of Compounds of Two NonmetalsTwo Nonmetals
Naming a compound with Naming a compound with only two nonmentals…only two nonmentals…
1.1. Write the name of the first Write the name of the first element along with the element along with the appropriate prefix.appropriate prefix.
2.2. Write the name of the second Write the name of the second element, modified to end in element, modified to end in ideide, , along with the appropriate prefix.along with the appropriate prefix.
Greek PrefixesGreek Prefixesmono-mono-11
di-di- 22
tri-tri- 3 3
tetra-tetra- 44
penta-penta- 55
hexa-hexa- 66
hepta-hepta- 77
octa-octa- 88
nona-nona- 99
deca- 10deca- 10
-ide endings-ide endingsHydrogen – hydrideHydrogen – hydrideCarbon – carbideCarbon – carbideNitrogen – nitrideNitrogen – nitrideOxygen – oxideOxygen – oxideFluorine – fluorideFluorine – fluorideSilicon – silicideSilicon – silicidePhosphorous – Phosphorous –
phosphidephosphide
Sulfur – sulfideSulfur – sulfide
Chlorine – chlorideChlorine – chloride
Arsenic – arsenideArsenic – arsenide
Selenium – selenideSelenium – selenide
Bromine – bromideBromine – bromide
Tellurium – tellurideTellurium – telluride
Iodine – iodideIodine – iodide
Examples …Examples …NONO22
PClPCl33
AsIAsI55
NN22OO44
II33NN77
nitrogen dioxidenitrogen dioxide
phosphorous trichloride phosphorous trichloride
arsenic pentiodide arsenic pentiodide
dinitrogen tetroxidedinitrogen tetroxide
triiodine heptanitridetriiodine heptanitride
Use Use mono-mono- sparingly sparingly
The prefix The prefix monomono- should only - should only be used to prevent confusion be used to prevent confusion
… … as in CO and COas in CO and CO22
Carbon monoxide and Carbon monoxide and carbon dioxidecarbon dioxide
You can write the formula from the You can write the formula from the name. The prefix tells the subscript.name. The prefix tells the subscript.
Nitrogen trichlorideNitrogen trichloride
NClNCl33
Carbon tetrachlorideCarbon tetrachloride
CClCCl44
Diphosphorous pentoxideDiphosphorous pentoxide
PP22OO55
Naming Binary Naming Binary Compounds Compounds
Containing a Metal Containing a Metal and a Nonmetaland a Nonmetal
The Stock SystemThe Stock System Named for Alfred Stock, a Named for Alfred Stock, a
German chemist of the nineteenth German chemist of the nineteenth century.century.
Add a Roman Numeral after the Add a Roman Numeral after the name of the positive element to name of the positive element to indicate its oxidation number.indicate its oxidation number.
Using the Stock System:Using the Stock System:1.1. Write the name of the positive Write the name of the positive
elementelement2.2. Add a Roman numeral Add a Roman numeral
corresponding to the oxidation corresponding to the oxidation number of the positive element (if number of the positive element (if necessary)necessary)
3.3. Write the name of the negative Write the name of the negative element, modified to end in -element, modified to end in -ideide
When is the Roman Numeral When is the Roman Numeral Necessary?Necessary?
When the metal has more than one When the metal has more than one oxidation number.oxidation number.
Metals in groups I A, II A, and III B, Metals in groups I A, II A, and III B, do not need Roman numerals.do not need Roman numerals.
Others metals have several oxidation Others metals have several oxidation numbers, and need Roman numerals.numbers, and need Roman numerals.
What is an oxidation number?What is an oxidation number?
An oxidation number is a An oxidation number is a number that tells us how an number that tells us how an element combines with other element combines with other elements.elements.
For ions, the For ions, the oxidation number is oxidation number is
the ionic charge.the ionic charge.
We can find oxidation We can find oxidation numbers in tables or we numbers in tables or we can predict them using can predict them using
the periodic table.the periodic table.
What does the Roman Numeral do?What does the Roman Numeral do?
The Roman numeral indicates the The Roman numeral indicates the oxidation number on a single metal oxidation number on a single metal atom, and differentiates between atom, and differentiates between several possible compounds.several possible compounds.
Consider: FeO and FeConsider: FeO and Fe22OO33
Both contain iron and oxygenBoth contain iron and oxygenBut, both cannot be But, both cannot be iron oxideiron oxide … …
… … so we use a Roman so we use a Roman numeral to differentiate numeral to differentiate
between the two between the two compounds.compounds.
First, determine the oxidation First, determine the oxidation number of iron in FeO …number of iron in FeO …
… … by starting with the negative by starting with the negative element, find the oxidation number element, find the oxidation number
of the positive element.of the positive element.
Since iron has an oxidation Since iron has an oxidation number of +2, FeO is named number of +2, FeO is named
iron (II) oxide.iron (II) oxide.
Likewise, for FeLikewise, for Fe22OO33 … …
First, determine the oxidation number First, determine the oxidation number of iron in Feof iron in Fe22OO33 … …
… … by starting with the negative by starting with the negative element, find the oxidation element, find the oxidation
number of the positive element.number of the positive element.
Since iron’s oxidation number is +3, Since iron’s oxidation number is +3, FeFe22OO33 is named is named iron (III) oxide.iron (III) oxide.
Remember …Remember …Only add a Roman Numeral if it is Only add a Roman Numeral if it is
needed.needed.It is needed when the metal has more It is needed when the metal has more
than one positive oxidation number.than one positive oxidation number.If the element has only one positive If the element has only one positive
oxidation number, you do not need a oxidation number, you do not need a Roman numeral.Roman numeral.
Writing formulas of Writing formulas of binary compounds binary compounds
of a metal and a of a metal and a nonmentalnonmental
The sum of the oxidation The sum of the oxidation numbers on all the atoms in numbers on all the atoms in a compound must equal a compound must equal zero.zero.
FeOFeO+2 –2 = 0+2 –2 = 0
Consider iron (II) oxide. Consider iron (II) oxide.
The sum is 0.The sum is 0.
Oxygen is –2 Oxygen is –2 and iron is +2.and iron is +2.
Now consider iron (III) oxideNow consider iron (III) oxide
FeFe22OO33
+3 -2+3 -2
In iron (III) oxide, In iron (III) oxide, the iron is +3 and the iron is +3 and the oxygen is –2. the oxygen is –2.
These don’t add up to zero.These don’t add up to zero.
Now consider iron (III) oxideNow consider iron (III) oxide
FeFe22OO33
+3 -2+3 -2+6+6 -6-6 = 0= 0
But, since there But, since there are two Fe atoms are two Fe atoms
and three O atoms, and three O atoms, we can multiply to we can multiply to
get the totals.get the totals.2 x 3 = 62 x 3 = 6
3 x –2 = -63 x –2 = -6 Now the sum is Now the sum is zero.zero.
Look at it another way:Look at it another way:
FeFe22OO33 = = Fe FeFe Fe O O OO O O+3+3 +3+3 -2-2 -2-2 -2-2
+6+6 -6-6+6 +6 –6–6 == 00
Now your are Now your are ready to write ready to write
formulasformulas
The Crisscross MethodThe Crisscross MethodSimple but effective, Simple but effective, ……most of the time.most of the time.Be aware of the potential Be aware of the potential
problems with this method.problems with this method.
Suppose you are writing the Suppose you are writing the formula for copper (II) chlorideformula for copper (II) chloride
First, write down First, write down the symbols:the symbols:
CuCu ClCl
Then write the oxidation Then write the oxidation numbers in copper (II) chloridenumbers in copper (II) chloride
CuCu ClCl
The oxidation The oxidation number of number of copper comes copper comes from the from the name.name.
-1-1+2+2
Get the Get the oxidation oxidation
number of number of chlorine chlorine from the from the
periodic table.periodic table.
Crisscross the numbers for the Crisscross the numbers for the formula of copper (II) chlorideformula of copper (II) chloride
CuCu ClCl+2+2 -1-1
2211
When you crisscross, When you crisscross, ignore the signs.ignore the signs.
11
Clean up the subscripts in the Clean up the subscripts in the formula of copper (II) chlorideformula of copper (II) chloride
CuCu ClCl+2+2 -1-1
22
Subscripts of 1 are invisible. Subscripts of 1 are invisible. (don’t even put the 1)(don’t even put the 1)
Now you have the formula of Now you have the formula of copper (II) chloridecopper (II) chloride
CuCu ClCl22
When is the “crisscross When is the “crisscross method” a problem?method” a problem?
When all the When all the subscripts are divisible subscripts are divisible by a number other than by a number other than 1.1.
Look at chromium (VI) oxideLook at chromium (VI) oxide
CrCr OOOxygen is Oxygen is always -2always -2
-2-2+6+6
The The oxidation oxidation number number of Cr is of Cr is +6+6
Look at chromium (VI) oxideLook at chromium (VI) oxide
CrCr OO+6+6 -2-2
6622
When you crisscross, both When you crisscross, both subscripts are divisible by 2.subscripts are divisible by 2.
Now, crisscross the oxidation Now, crisscross the oxidation numbers.numbers.
____ 22
____ 22
Look at chromium (VI) oxideLook at chromium (VI) oxide
CrCr OO+6+6 -2-2
6622
Divide each subscript by 2.Divide each subscript by 2.
Look at chromium (VI) oxideLook at chromium (VI) oxide
CrCr OO33
This is the correct formulaThis is the correct formula
Remember, 1’s are invisible.Remember, 1’s are invisible.
Remember: reduce the Remember: reduce the subscripts to their subscripts to their
smallest whole-number smallest whole-number values.values.
Unless there’s a really Unless there’s a really good reason not to.good reason not to.
Some Exceptions:Some Exceptions:
NN22OO44
HgHg22ClCl22
CC22HH66
CC66HH66
The The “ic/ous” Method “ic/ous” Method
of Naming of Naming CompoundsCompounds
The “ic/ous” method …The “ic/ous” method …
… … is an archaic method, but still in is an archaic method, but still in use today by the chemical industryuse today by the chemical industry
… … uses the uses the –ic–ic or – or –ousous suffixes on suffixes on the name of the metal.the name of the metal.
… … may use the Latin root may use the Latin root … … uses prefixes like uses prefixes like hypo-hypo- & & per-per-
Name and Name and
Latin RootLatin Root
Lower Ox. Lower Ox. NumberNumber
Higher Ox. Higher Ox. NumberNumber
iron iron
ferrumferrum
ferrous ferrous
Fe Fe 2+2+
ferric ferric
FeFe3+3+
copper copper
cuprumcuprum
cuprous cuprous
CuCu++
cupric cupric
CuCu2+2+
mercurymercury mercurous mercurous
HgHg222+2+
mercuric mercuric
HgHg2+2+
ICICOUSOUS
Higher oxidation numberHigher oxidation number
Lower oxidation numberLower oxidation number
ExamplesExamples … …
FeClFeCl22
CuOCuOFeNFeNCuCu33PPHgSHgSHgHg22ClCl22
Ferrous chlorideFerrous chlorideCupric oxideCupric oxideFerric nitrideFerric nitrideCuprous phosphideCuprous phosphideMercuric sulfideMercuric sulfideMercurous chlorideMercurous chloride
Write the formula …Write the formula …
Ferric bromideFerric bromideCupric nitrideCupric nitrideFerrous chlorideFerrous chlorideMercuric oxideMercuric oxideMercurous iodideMercurous iodideStannous fluorideStannous fluoride
FeBrFeBr33
CuNCuN33
FeClFeCl22
HgOHgO
HgHg22II22
SnFSnF22
Click on the links below Click on the links below for Parts II or III for Parts II or III
Part III – Naming Acids and Bases
Part II – Polyatomic ions
