Chapter 5 Nomenclature

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 classes Compounds containing a metal & non-metal 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 follows The cation is named first and the anion second. A simple cation takes its name from the name of the element. 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 following MgI2 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 follows Cation is named using element name Charge is indicated by a Roman Numeral after the cation name 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 follows The 1st element in the formula is named first. The full element name is used. The 2nd element in the formula is named as if it were an anion (-ide ending) Prefixes are used to denote the number of atoms present The prefix mono- is never used for naming the first element

Prefixes one mono two di three tri four tetra five penta six hexa seven hepta eight 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 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

Oxyanions Per- -ate SO5-2 Persulfate PO5-3 Perphosphate NO4-1 Pernitrate ClO4-1 Perchlorate -ate SO4-2 Sulfate PO4-3 Phosphate NO3-1 Nitrate ClO3-1 Chlorate -ite SO3-2 Sulfite PO3-3 Phosphite NO2-1 Nitrite ClO2-1 Chlorite Hypo- -ite SO2-2 Hyposulfite PO2-3 Hypophosphite NO-1 hyponitrite ClO-1 Hypochlorite -ide S-2 Sulfide P-3 Phosphide N-3 Nitride Cl-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 Does not contain oxygen: acid is named with the prefix hydro- and the suffix –ic Example: HCl Hydrochloric acid 2. Does contain oxygen: acid is named with the root name of the central element of the anion and a suffix a. When the anion name contain –ate, the suffix –ic is used i.e. H2SO4 SO4 is sulfate sulfuric acid b. When the anion name contains –ite, the suffix –ous is used i.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