Chemistry 101
Chapter 5
Nomenclature
Metal (usually): loses one, two or three electrons and in losing electrons, the atom becomes a
positively charged ion called a Cation (Na+, Ca2+, Mg2+).
Nonmetal (usually): gains one, two or three electrons and in gaining electrons, the atom
becomes a negatively charged ion called an Anion (Cl-, O2-, S2-).
Ionic bonds: ionic bonds usually form between a metal and a nonmetal. In ionic bonding,
electrons are completely transferred from one atom to another. In the process of either losing
or gaining negatively charged electrons, the reacting atoms form ions. The oppositely charged
ions are attracted to each other by electrostatic forces, which are the basis of the ionic bond.
Na → Na+ + e-
Na+ ↔ Cl- → NaCl
-
Cl + e → Cl
Note: there are enormous differences between the chemical and physical properties of an
atom and those of its ion(s). For example sodium is a soft metal and it reacts violently with
water. Chlorine is a gas and it is very unstable and reactive. Both sodium and chlorine are
poisonous. However, NaCl (common table salt made up of Na+ and Cl-) is quite stable and
unreactive.
Binary ionic compounds (a metal and a non-metal):
Naming Type I (Monatomic cations): the metal present forms only one type of cation (main
group elements).
Name of metal + “ion”
Na+
Sodium ion
Ba2+
Barium ion
Al3+
Aluminium ion
Naming Type II (Monatomic cations): If the metal present can form two (or more) cations
that have different charges (most transition and inner transition elements), we show the charge
with the Roman numeral immediately following the name of the metal (for Systematic name
or IUPAC (International Union of Pure and Applied Chemistry)). We can also use the suffix
“-ous” to show the smaller charge and the suffix “-ic” to show the larger charge (for
Common name).
Ion
+
Cu
Cu2+
Fe2+
Fe3+
Hg+
Hg2+
Sn2+
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Systematic name
Common name
Copper(I) ion
Copper(II) ion
Iron(II) ion
Iron(III) ion
Mercury(I) ion
Mercury(II) ion
Tin(II) ion
Cuprous ion
Cupric ion
Ferrous ion
Ferric ion
Mercurous ion
Mercuric ion
Stannous ion
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Sn4+
Cr2+
Cr3+
Co2+
Co3+
Pb2+
Pb4+
Tin(IV) ion
Chromium(II)
Chromium(III)
Cobalt(II)
Cobalt(III)
Lead(II)
Lead(IV)
Stannic ion
Chromous ion
Chromic ion
Cobaltous ion
Cobaltic ion
Plumbous ion
Plumbic ion
Naming Monatomic anions: we add “-ide” to the step part of the name.
Anion
Stem name
Anion name
FClBrIS2O2N3P3-
fluor
chlor
brom
iod
sulf
ox
nitr
phosph
Fluoride
Chloride
Bromide
Iodide
Sulfide
Oxide
Nitride
Phosphide
Naming Polyatomic ions: we use the prefixes “di-”, “tri-” and so forth to show the presence
of more than one hydrogen (the prefix “bi” is used to show the presence of one hydrogen).
Polyatomic ion
+
Name
Polyatomic ion
2-
NH4
OH-
Ammonium
Hydroxide
SO3
SO42-
NO2-
Nitrite
HSO3-
NO3CH3COOO22MnO4CrO42Cr2O72CO32-
Nitrate
Acetate
Peroxide
Permanganate
Chromate
Dichromate
Carbonate
Hydrogen carbonate
(bicarbonate)
HSO4PO33PO43HPO42H2PO4ClOClO2ClO3ClO4-
HCO3-
Name
Sulfite
Sulfate
Hydrogen sulphite
(bisulfite)
Hydrogen Sulfate (bisulfate)
Phosphite
Phosphate
Hydrogen phosphate
Dihydrogen phosphate
Hypochlorite
Chlorite
Chlorate
Perchlorate
Oxyanions: several series of polyatomic anions exist that contain an atom of a given element
and different numbers of oxygen atoms. These anions are called oxyanions. When there are
two members in such a series, the name of the one with the smaller number of oxygen atoms
ends in “–ite”, and the name of the one with the larger number ends in “-ate”:
SO32-
Sulfite
2-
SO4
PO33PO43-
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Sulfate
Phosphite
Phosphate
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When more than two oxyanions make up a series, “hypo-” (less than) and “per-” (more than)
are used as prefixes to name the members of the series with the fewest and the most oxygen
atoms:
ClOClO2ClO3ClO4-
Hypochlorite
Chlorite
Chlorate
Perchlorate
Binary ionic compounds: matters are electrically neutral (uncharged). The total number of
positive charges must equal the total number of negative charges. The subscripts in the
formulas for ionic compounds represent the ratio of the ions.
Na+
Cl- → NaCl
Ba2+
Ca2+
O2- → Ba2O2
Cl- → CaCl2
Al3+
S2- → Al2S3
we must reduce to lowest terms:
BaO
Naming binary ionic compounds: Name of cation (metal) + name of anion
Note: We generally ignore subscripts in naming binary ionic compounds.
Note: many transition metals form more than one positive ion. We use Roman numerals in
the name to show their charges.
NaCl Sodium chloride
CuO
CaO
Calcium oxide
FeCl2 Iron(II) chloride (Ferrous chloride)
Copper(II) oxide (cupric oxide)
MgCO3
AlCl3 Aluminium chloride
Magnesium carbonate
NaOH
Sodium hydroxide
Binary covalent compounds (two nonmetals):
Naming Type III (binary covalent compounds): name the less electronegative element (the
first element in the formula) + name the more electronegative element (the second element in
the formula) + adding “-ide” to the stem part of the name. We use the prefixes mono-, di-, tri-,
tetra-, penta-, hexa-, hepta-, octa-, nona-, deca- to show the number of atoms of each element.
Note: the prefix “mono-” is omitted for the first atom named and it is rarely used with the
second atom.
Note: we drop “a” when following a vowel.
SO3
Sulfur trioxide
N2O4 Dinitrogen tetroxide
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PCl5
OF2
Phosphorus pentachloride
Oxygen difluoride
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Naming binary acids: we use the name of the anion that they produce when they dissociate.
We replace the suffix “-ic acid” instead of “-ide ion”. Then, we add it after the prefix “hydro“.
HF
HCl
anion: fluoride ion
anion: chloride ion
acid name: hydrofluoric acid
acid name: hydrochloric acid
Naming ternary acids: we use the name of the polyatomic anion that they produce when they
dissociate. For the smaller charge, we replace the suffix “-ous acid” instead of “-ite ion” and
for the larger charge, we replace the suffix “-ic acid” instead of “-ate ion”.
NO2-: nitrite ion
NO3-: nitrate ion
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HNO2: nitrous acid
HNO3: nitric acid
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