Chapter 5Nomenclature

History of Naming

• When chemistry first came about, there was no general naming system.

• Scientists used common names like laughing gas, epsom salt, and milk of magnesia

• This became impractical with the discovery of over 4 million chemical compounds

• Therefore scientists developed a standardized system known as nomenclature

Naming Binary Compounds

• Binary compounds are composed of two elements

• There are two classes1. Compounds containing a metal & non-metal2. Compounds containing two non-metals

Naming Binary Ionic Compounds

• Metals and non-metals combine to form compounds that contain ions (NaCl)

• The metal loses 1 or more electrons to become a cation

• The non-metal gains 1 or more electrons to became an anion

• These are known as binary ionic compounds (ionic compounds for short)

Naming Binary Ionic Compounds

• There two types of binary ionic compounds– Type I: The metal present only forms one type of

cation (Group IA, 2A, Al)– Type II: The metal can form two or more cations

that have different charges (mostly transition metals like chromium, copper, etc)

Naming Type I Binary Ionic Compounds

• The rules are as follows1. The cation is named first and the anion second.2. A simple cation takes its name from the name of

the element.3. A simple anion takes the root name of the

element and adds –ide to the end

Example 1

• Name the following: NaCl– Rule 2: Name of cation is name of element:

Sodium– Rule 3: Name of anion is element root with –ide:

chloride– Rule 1: Cation first, anion second: Sodium Chloride

Example 2

• Name the following: AlCl3 – Rule 2: Name of cation is name of element

– Rule 3: Name of anion is element root plus –ide:

– Rule 1: Cation first, anion second

Now you try

• Name the following1. MgI2

2. CaS

Now we will try a few examples…

Naming Type II Binary Ionic Compounds

• There are many metals that can form more than one type of cation– Lead can form Pb2+ or Pb4+

– Iron can form Fe2+ or Fe3+

– Gold can form Au+ or Au3+

Naming Type II Binary Ionic Compounds

• Take AuCl vs. AuCl3

• If we named this using the rules for Type I compounds, Gold chloride, we wouldn’t know which formula the name was referring to

• Chemists have solved this problem by using Roman Numerals to indicate the charge on a cation

Naming Type II Binary Ionic Compounds

• Consider FeCl2

• Fe can form Fe2+ or Fe3+

• Compounds containing ions must have a net charge of zero

• Fe (?) Cl (-1 x 2 = -2)• Fe must 2+• We name this compound Iron(II) chloride• Note: The Roman Numerals indicate the charge,

NOT the number of atoms present

Naming Type II Binary Ionic Compounds

• The rules are as follows1. Cation is named using element name2. Charge is indicated by a Roman Numeral after

the cation name3. Anion is named using element root name and

adding –ide

Example 1

• Name the following: CuCl• We know that chlorine always forms -1 anions• Compounds containing ions must have a net

charge of zero• Therefore copper must have a +1 charge• Name: Copper(I) chloride

Example 2

• Name the following Fe2O3

• We know that oxygen always forms -2 anions, providing a total charge of -6 (-2 x 3)

• Compound must have a net charge of 0• Therefore iron must contribute +6 worth of

charge• There are two iron atoms present, each having a

charge of +3• Name: Iron(III) oxide

Now you try

• PbCl4

• MnO2

• Now we will try a few examples…

Naming Binary Compounds that Contain Only Non-metals (Type III)

• Type III compounds only contain non-metals• These are known as non-ionic or covalent

compounds

Naming Type III Binary Compounds

• The rules are as follows1. The 1st element in the formula is named first.

The full element name is used.2. The 2nd element in the formula is named as if it

were an anion (-ide ending)3. Prefixes are used to denote the number of atoms

present4. The prefix mono- is never used for naming the

first element

Prefixes

one monotwo dithree trifour tetrafive pentasix hexaseven heptaeight octa

Example 1

• Name the following BF3

– Rule 1: Name the first element: boron– Rule 2: Name the second element like an anion:

fluoride– Rule 3 & 4: Use prefixes for number of atoms

• 1 boron atom (don’t use mono): boron• 3 fluorine atoms: trifluoride

Name: boron trifluoride*Note: When the 2nd element is oxygen, we drop the a or o

from the end of the prefix to avoid strange pronunciation

Example 2

• Name the following N2O5

– Rule 1: Nitrogen– Rule 2: oxide– Rule 3 & 4• 2 nitrogen: dinitrogen• 5 oxygen: pentoxide

Name: dinitrogen pentoxide

Now you try

• CCl4

• IF5

• Now we will try a few examples

Polyatomic Compounds

• Polyatomic Ions are charge entities composed of several atoms bound together

• Unfortunately, the names of most polyatomic atoms need to memorized

Oxyanions

• Oxyanions contain an atom of a given element and different numbers of oxygen atoms

• Example SO4-2

OxyanionsPer- -ate SO5

-2

PersulfatePO5

-3

PerphosphateNO4

-1

PernitrateClO4

-1

Perchlorate-ate SO4

-2

SulfatePO4

-3

PhosphateNO3

-1

NitrateClO3

-1

Chlorate-ite SO3

-2

SulfitePO3

-3

PhosphiteNO2

-1

NitriteClO2

-1

ChloriteHypo- -ite SO2

-2

HyposulfitePO2

-3

HypophosphiteNO-1

hyponitriteClO-1

Hypochlorite

-ide S-2

SulfideP-3

PhosphideN-3

NitrideCl-1

Chloride

Some other common polyatomic ions

• NH4+ Ammonium

• OH- Hydroxide• CN- Cyanide• CO3

-2 Carbonate

Naming using polyatomic ions

• Following typical naming rules– Cation named first, anion named second– Name of cation is element name– Name of anion is anion name– If a metal is present that is multivalent, we need

to use Roman Numerals to indicate charge

Example 1

• Na2SO4

– Name of cation is name of element: Sodium– Name of anion is anion name: sulfate– We know the charge on sodium, so we don’t need

Roman numerals– Name: Sodium sulfate

Example 2

• Fe(NO3)3

– Name of cation is name of element: Iron– Name of anion is anion name: nitrate– Need to calculate charge on copper: +3– Name: Copper (III) nitrate

You try

• Mn(OH)2

• Na2SO3

Naming Acids

• When dissolved in water, certain compounds produce H+ ions

• We call these compounds acids• Acids can be viewed as a compound with one

or more H+ ions and an anion• Rules for naming depend on whether anion

contains oxygen

Naming Acid Rules

1. Does not contain oxygen: acid is named with the prefix hydro- and the suffix –icExample: HCl Hydrochloric acid

2. Does contain oxygen: acid is named with the root name of the central element of the anion and a suffixa. When the anion name contain –ate, the suffix –ic is usedi.e. H2SO4 SO4 is sulfate sulfuric acid

b. When the anion name contains –ite, the suffix –ous is usedi.e. H2SO3 SO3 is sulfite sulfurous acid

Example 1

• HBr– Does not contain oxygen– Hydrobromic acid

Example 2

• HNO3

– Contains oxygen– NO3 is nitrate– Nitric acid

You try

• HI• H3PO3