K.D. McMahon
Reseda High School
Chemical Nomenclature
Summary:
The language of chemistry must be learned by every student of chemistry. This unit
discusses the rules governing chemical nomenclature.
Objectives:
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Discuss the nomenclature used to name elements in their "natural" state.
Describe type I and II ions and their nomenclature.
Describe the nomenclature used to name compounds from type I and II ions.
Discuss acids and their names.
I. Elements In Their Natural State
Most elements are very reactive. Reactive elements tend to combine with other elements
to form compounds. Some elements combine with themselves to form diatomic
molecules.
Examples: O2, H2, N2, Cl2
A few nonreactive elements can be found in their natural states. Gold, silver, and
platinum (noble metals) are sometimes found in their pure form. The nonreactive nature
of these metals explains why they are used in jewelry (they do not tarnish) and
electronics they do not form oxides which increases resistances).
The Noble Gases are always found in their elemental state.
II. Ions
Ions are atoms which are electrically charged. A neutral atom has an equal number of
protons and electrons.
If an atom loses 1 or more electrons the atom becomes a positive ion or cation. A cation
is named using the name of the parent ion.
Examples:
Na --> Na+ +1 e- (Sodium ion)
Mg --> Mg+2 + 2e- (Magnesium ion)
Al --> Al+3 + 3e- (Aluminum ion)
If an atom gains 1 or more electrons it becomes a negatively charged ion or an anion. An
anion is named by taking the root name of the atom and adding the suffix -ide.
Examples:
Cl + 1e- --> Cl- (Chloride)
O + 2e- --> O-2 (Oxygen)
S+ 2e- --> S-2 (Sulfide)
The Periodic Table is helpful in determining the ions formed by atoms.
All of the metallic elements produce cations. The group 1, 2, and 3 elements produce
cations with +1, +2, and +3 charges, respectively. The transition elements produce
cations with various charges.
Nonmetals tend to produce anions. The group 6 elements gain 2 electrons to form-2
anions. The group 7 elements gain 1 electron to form -1 anions.
Cations and anions can combine to form ionic compounds. Ionic compounds must be
electrically neutral. The chemical formula of an ionic compound shows the proportion of
cations and anions needed to achieve neutrality.
To write chemical formula for ionic compounds:
Find the lowest common multiple between the two ions:
Example:
Compound formed by Al+3 & O-2
LCM = 6
# of Al = 6/3 = 2
# of O = 6/2 = 3
formula = Al2O3
Or use superscripts to subscripts.
Al2O3
Properties of ionic compounds:
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Crystalline structure.
Neutral, nonconductor of electricity.
High melting point.
Soluble in water.
Able to conduct electricity in liquid state or when dissolved in water.
III. Naming Compounds
Naming Compounds Made of a Metal and a Nonmetal:
The cation is always named first and the anion second. The simple cation takes its name
from the name of the element. The simple anion is named by taking the first part of the
element and adding "-ide."
Examples:
NaCl = sodium chloride
CaO = calcium oxide
CsBr= cesium bromide
Al2O3 = aluminum oxide
Naming Compounds Made of a Transition Metal and a Nonmetal:
A number of transition metals produce more than one type of cation. Chemists use
Roman numerals to identify the cations. An older system of naming these cations uses
the suffix "-ous" to identify the lower charged cations and "-ic"to identify the higher
charged ion.
Ions
Au+
Au+3
Fe+2
Fe+3
Cu+
Cu+2
Co+2
Co+3
Systemic Name
Gold (I)
Gold (II)
Iron (II)
Iron (III)
Copper (I)
Copper (II)
Cobalt (II)
Cobalt (III)
Traditional Name
Aurous
Auric
Ferrous
Ferric
Cuprous
Cupric
Cobaltous
Cobaltic
Cr+2
Cr+3
Ni+2
Ni+3
Sn+2
Sn+4
Sb+3
Sb+5
Pb+2
Pb+4
Hg2+2
Hg+2
Some transitions metals
with one ionization
Zn+2
Ag+
Cd+2
Chromium (II)
Chromium (III)
Nickel (II)
Nickel (III)
Tin (II)
Tin (IV)
Antimony (III)
Antimony (V)
Lead (II)
Lead (IV)
Mercury (I)
Mercury (II)
Chromous
Chromic
Nickelous
Nickelic
Stannous
Stannic
Antimonous
Antimonic
Plumbous
Plumbic
Mercurous
Mercuric
zinc
silver
Cadmium
To name type II ionic compounds (compounds that include metals with more than one
type of cation) use the systemic or traditional cation name and the anions "-ide" name.
Examples:
FeCl2: iron (II) chloride or ferrous chloride
PbO2: lead (IV)oxide or plumbic oxide
Note: The formula for lead (IV) oxide has
been simplified to PbO2: Pb2O4 ---> PbO2
Ionic compounds are reduced to their
lowest terms.
Naming Compounds Made of Two Nonmetals:
The first element in the formula is named first; the full element name is used. The second
element is named as though it were an anion. Prefixes are used to denote the number of
atoms present.
Mono
Di
Tri
Tetra
Penta
1
2
3
4
5
Hexa
Hepta
Octa
Nona
Deca
The prefix "mono" is never used for naming the first element.
Examples:
6
7
8
9
10
BF3: boron trifluoride
NO: nitrogen monoxide
N2O5: dinitrogen pentoxide
CCl4: carbon tetrachloride
Naming Compounds That Contain Polyatomic Ions:
A polyatomic ion is an ion made of several atoms.
Ion
NH4+
NO2-
Name
Ammonium
Nitrite
Ion
CO3-2
HCO3-
NO3SO3-2
SO4-2
HSO4OHCNPO4-3
HPO4-2
H2PO4-
Nitrate
Sulfite
Sulfate
Hydrogen sulfate
Hydroxide
Cyanide
Phosphate
Hydrogen phosphate
Dihydrogen
phosphate
ClOClO2ClO3ClO4C2H3O2MnO4Cr2O7-2
CrO4-2
O2-2
Name
Carbonate
Hydrogen carbonate
or bicarbonate
Hypochlorite
Chlorite
Chlorate
Perchlorate
Acetate
Permanganate
Dichromate
Chromate
peroxide
Oxyanions are a series of anions with a given element combined with different numbers
of oxygen atoms. When there are two members in a series:
• the name of the one with the smaller number of oxygen atoms end in "-ite."
• the name of the one with the larger number of oxygen atoms ends in "-ate."
Examples:
NaClO: sodium hypochlorite
Ca(ClO4)2: calcium perchlorate
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 most
oxygen atoms, respectively. Also note that the other halogens (Bromine, Iodine, and
Fluorine) can also form this series.
When naming ionic compounds containing polyatomic ion's name each component of the
compound.
Examples:
Na2SO4: sodium sulfate
KH2SO4: potassium dihydgrogen sulfate
Fe(NO3)3: iron (III) nitrate
Naming Acids:
Acids are substances which when dissolved water produce H+ ion. An acids is a
molecule containing one or more H+ ions attached to an anion. The rules for naming
acids depend on whether the anion contains oxygen.
Examples:
HF: hydrofluoric acid
HNO2: nitrous acid
HCN: hydrocyanic acid
H3PO4: phosphoric acid
Question #1:
a.) CaS
g.) ZnCl2
n.) K2Cr2O7
t.) HBr
Name the following compounds:
b.) AlI3
c.) Hg2O
d.)FeBr3
h.) Li3N
i.) Ag2S
k.) MnO2
o.) S4N4
p.) H2O
q.) Icl
u.) HBrO2
v.) H2S
w.) H2SO4
e.) Cr2O3
l.) KClO4
r.) SO2
x.) H2SO3
f.) NaH
m.) Pb(NO3)2
s.) NH4NO3
y.) HI
Question #2: Write formulas for each of the following:
a.) cesium bromide
b.) silicon tetrachloride
c.) ammonium chloride
d.) chlorine monoxide
e.) chlorine trifluoride
f.) sulfur hexafluoride
g.) chromium (II) carbonate h.) lithium nitride
i.) perchloric acid
j.) cupric nitrate
k.) lead (IV) sulfide
l.) ammonium acetate
m.) stannous fluoride
n.) iodous acid
o.) carbonic acid
p.) acetic acid
q.) sodium dihydrogen phosophate
r.) hydrosulfuric acid
s.) diphosphorus pentoxide t.) selenium tetrabromide
u.) potassium cyanide
v.) cyanic acid
w.) mercury (I) bromide
x.) sodium sulfite
y.) perbromic acid
z.) calcium hydrogen sulfate