2.4: Chemical Nomenclature
1. Molecular Compounds
Prefixes
Naming:
• Put the appropriate prefix IN FRONT of the element name
• Exception: Do not use mono- on the FIRST element
• Change the ending of the second element to “ide”
• Many also have common names
1 – mono
2 – di
3 – tri
4 – tetra
5 – penta
6 – hexa
7 – hepta
8 – octa
9 – nona
10 -- deca
Formulas:
• Use the prefix to determine the subscript
• DO NOT reduce
Common Names:
Ammonia _________
Methane _________
Water _________
Ozone _________
Practice
Trinitrogen hexasulfide
NO
Carbon dioxide
P Br
Tetrafluorine octachloride
SI
2
9
3
2. Ionic Compounds
a) Simple Binary Compounds (2 different elements – metal and non-metal)
Naming:
• Write the metal first, then the non-metal
• Change the ending of the non-metal to –ide
Formulas:
• Write the symbol for each element in the correct order (metal first)
• Write the ionic charge above each symbol (by using the group number)
• Note: Zn2+ and Ag+
• Criss-cross the numbers from the charges to the opposite element
• Simplify (reduce) if necessary
Practice
Beryllium fluoride
CaCl
Calcium sulfide
MgO
Aluminum oxide
K3P
2
b) Multivalent Binary Compounds (the metal has more than one ionic charge)
Naming
• Two methods to name these:
a) Stock method – uses roman numerals
• Write the roman number that corresponds with
the correct charge AFTER the metal name
b) Classical method – the “ous-ic” system
• uses latin names of elements
• “ous” = lowest valence
• “ic” = highest valence
Formulas
• Use the criss-cross method and reduce
Multivalent metals
Charges
Copper
Tin
Iron
Nickel
Manganese
Gold
Lead
Mercury
Cu+ Cu2+
Sn2+ Sn4+
Fe2+ Fe3+
Ni2+ Ni3+
Mn2+ Mn4+
Au+ Au3+
Pb2+ Pb4+
Hg+ Hg2+
Examples
Latin Name
Remove “um”
ending
Lower
Valence
Lower Valence
Name (-ous)
Higher
Valence
Higher valence
Name (-ic)
Cuprum (Cu)
Cupr
1+
Cuprous
2+
Cupric
Ferrum (Fe)
Ferr
2+
3+
Stannum (Sn)
Stann
2+
4+
Plumbum (Pb)
Plumb
2+
4+
Practice
Copper (II) fluoride
Tin (IV) sulfide
Mercury (I) oxide
Stannous phosphide
Ferrous oxide
SnCl
2
Fe2S3
PbS
2
c) Polyatomic Compounds
• Polyatomic ions: ions that contain more than one type of atom
• Can be + or – charged
• Will combine with an oppositely charged ion to make a compound
• See chart for polyatomic ions
Naming
• Do not change endings of polyatomic ions. Otherwise, same ionic naming rules apply
Formulas
• Use criss-cross method
• DO NOT alter the subscripts of the polyatomic ion
• Put the polyatomic in brackets, criss-cross the number to the OUTSIDE of these brackets
• Simplify if necessary
Practice
Copper (II) chlorate
NaCN
Zinc sulfate
Fe(NO )
Magnesium hydroxide
NH OH
3 3
4
d) Derivatives of Polyatomic Ions
• Other polyatomic ions may have different amounts of oxygen atoms
Naming
• Name the original ion
• Add prefix “per-” if there is 1 MORE oxygen
• Change suffix to “-ite” if there is 1 LESS oxygen
• Add prefix “hypo-” and change suffix to “-ite” if there are 2 LESS oxygen
Formulas
• Add or subtract the appropriate number of oxygen from the original ion
• Overall charge of ion does NOT change
Example
Chlorate
ClO
3
Practice (ions only)
Practice (compounds)
Iodite
Iron (II) hyposulfite
Hypophosphite
Lithium chlorite
persulfate
NaIO
BrO2-
K PO
3. Acids
a) Binary Acids
• An acid which is made by dissolving certain gases in water
• Acids always start with a hydrogen that acts like a metal
• A binary acid is formed from a binary compound
• The subscript (aq) is used to denote the acid
• (aq) = aqueous = dissolved in water
Naming
• Has the same formula as the gas, but a different name (hydro_______ic acid)
Formulas
• Use “criss-cross” – H+ is the cation (H acts like a metal)
3
5
Practice
Name of Gas
Formula
Name of Acid
Formula
Hydrogen chloride
HCl (g)
Hydrochloric acid
HCl (aq)
HBr (g)
Hydroiodic acid
Hydrogen fluoride
H2S (aq)
b) Oxyacids
• Contain oxygen, hydrogen, plus another element
Naming
• Remove “-ate” and add “-ic acid”
Formulas
• Combine hydrogen with the corresponding polyatomic ion
Practice
Original Polyatomic Ion
Acid Name
Nitrate
Nitric Acid
Chlorate
Chloric Acid
Sulfate
Sulfuric Acid
Carbonate
Carbonic Acid
Phosphate
Phosphoric Acid
Acetate
Acetic acid
Chromate
Chromic Acid
Dichromate
Dichromic Acid
Acid Formula
c) Derivatives of Oxyacids
• Many of the oxyacids have various forms, or derivatives
Naming
• Similar to derivatives of polyatomic ions and “ous/ic” system
• Start with original acid ( - ic acid)
• Add prefix “per-” if there is 1 MORE oxygen
• Change suffix “-ic” to “-ous” if there is 1 LESS oxygen
• Add prefix “hypo-” and change suffix “ic” to “-ous” if there are 2 LESS oxygen
Formulas
• Use prefixes and suffixes to determine the correct number of oxygen atoms
Example
Practice
Nitrous Acid
Chloric Acid
HClO
3
Percarbonic Acid
H PO
3
2
H CO
2
d) Acid Salts
• Formed when only some of the hydrogen atoms in an acid are replaced by a metal
Naming
• If 1 hydrogen replaced – use hydrogen or bi
• If more than 1 hydrogen replaced – use a prefix to indicate the number of hydrogen atoms that
are present
Formulas
• Will see hydrogen in the middle of the name – this is a part of a polyatomic ion (see chart)
• Use criss-cross
Practice
Sodium hydrogen carbonate
(OR sodium bicarbonate)
Calcium dihydrogen phosphate
Potassium biphosphate
LiHSO
3
Ba(HSO )
4 2
4. Hydrates
• Not all substances are “dry” – many have traces of water in them
• Even if we try to evaporate certain substances, some of the water remains
Naming
• Name the compound normally, followed by ______________hydrate (use the appropriate prefix
for the number of water molecules)
Formulas
• Write the formula for the compound first, followed by a dot and the number of water molecules
present
Practice
Copper (II) sulfate pentahydrate
Barium hydroxide octahydrate
CoCl  6 H O
2
2
Na PO  2 H O
3
3
2