Chemistry 20 – Unit 3
Elements, Compounds and Nomenclature
the term “nomenclature” refers to “naming”
•
chemical nomenclature is the organized system
•
chemists use to name substances and write their
chemical formulas
when writing any formula for any substance we
•
first assume that the substance exists on its own, at
room temperature
if special conditions exist, states of matter are
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adjusted
Naming Pure Elements
Metals
when naming metals, we simply state the
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elemental name given on the periodic table
when writing the formula for any pure metal we
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simply write the elemental symbol (no subscripts)
inclusion of states of matter is very important, so
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we must always indicate a solid state, the exception
being mercury, Hg(l)
Chemistry 20 – Unit 3 Page 1 Overhead Notes
Elements, Compounds and Nomenclature

Nonmetals
when naming nonmetals, we simply state the
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elemental name given on the periodic table
when writing the formula for any pure nonmetal
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we write the elemental symbol with subscripts for
some of the nonmetals, because we must also be
aware of how it exists at room temperature
for most nonmetals, you’ve just got to memorize
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their formulas and their natural states of matter
all nobles gases are monatomic: He(g) , Ne(g) , Ar(g) ,
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Kr(g) , Xe(g) , Rn(g)
diatomic elements include:
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• nitrogen – N2(g)
• oxygen – O2(g)
• all halogens: fluorine – F2(g)
chlorine – Cl2(g)
bromine – Br2(l)
iodine – I2(s)
astatine – At2(s)
polyatomic elements include:
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• phosphorous – P4(s)
• sulfur – S8(s)
all other nonmetals are monatomic and solid,
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except bromine
Chemistry 20 – Unit 3 Page 2 Overhead Notes
Elements, Compounds and Nomenclature

Naming Compounds
a compound is a pure substance made by combining
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at least two different elements in a specific ratio
Ionic Compounds
an ionic compound is formed by taking one
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metallic ion and combining it with one
nonmetallic ion or a complex ion
Binary Ionic Compounds
only one metallic ion and one nonmetallic ion are
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combined
Process for Creating the Formula:
find the elements
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list their ions
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place positive ions (cations) first, followed by
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negative ions (anions)
criss-cross their charges to create the correct
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ratio of each element and simplify charges
(reduce)
the state of matter for all ionic compounds is
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solid
Chemistry 20 – Unit 3 Page 3 Overhead Notes
Elements, Compounds and Nomenclature

Naming Ionic Compounds
the first element gets its normal elemental name
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as found on the periodic table
the second element’s name has an “ide” ending
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(regardless of the ratios found in the formula)
Examples:
sodium and chlorine
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Na+ and Cl –
Na + Cl –
Na –1 Cl +1
NaCl (one’s are ignored)
NaCl(s)
sodium chloride
magesium and iodine
•
Mg 2+ and I –
Mg 2+ I –
Mg –1 I 2+
MgI2
MgI2(s)
magnesium iodide
Chemistry 20 – Unit 3 Page 4 Overhead Notes
Elements, Compounds and Nomenclature

oxygen and aluminum
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Al 3+ and O 2–
Al 3+ O 2–
Al –2 O +3
Al2O3
Al2O3(s)
aluminum oxide
oxygen and calcium
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Ca 2+ and O 2–
Ca 2+ O 2–
Ca –2 O +2
Ca2O2
*note: subscripts are simplified for
ionic compounds
CaO
CaO(s)
calcium oxide
Chemistry 20 – Unit 3 Page 5 Overhead Notes
Elements, Compounds and Nomenclature

Creating the Formula and Naming Ionic
Compounds Using Complex Ions
when a simple positive ion is combined with a
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complex ion the process is as follows:
• list both positive and negative ions
• combine both
• use brackets for the complex ion
• criss-cross their charges
• simplify subscripts
when naming the compound, use the normal first
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name for the metallic ion and copy the given name
of the complex ion, which is found in the complex
ion table
Examples:
calcium and hydroxide
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Ca 2+ and OH –
Ca 2+ and (OH) –
Ca –1 (OH) 2+
Ca1(OH)2
since 1’s are not required
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Ca(OH)2(s)
note that if a 1 should appear after the
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brackets, the brackets are not required
Chemistry 20 – Unit 3 Page 6 Overhead Notes
Elements, Compounds and Nomenclature

Naming Ionic Compounds Using Multiple Ion
Charges
some metallic ions have more than one charge
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for example, iron has Fe2+ and Fe3+
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in these cases it is necessary to actually state which
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ion is being used
Roman numerals are used after each multiple-
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charged ion
Example
iron and oxygen
Fe2+ and O2–
FeO(s) named iron (II) oxide
or
Fe3+ and O2–
Fe2O3(s) named iron (III) oxide
some tables may use old, “classical” names that
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end with “ic” or “ous”
“ic” ending is for the ion that has the greater
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charge
Example
Fe3+ is also called ferric
Fe2+ is also called ferrous
FeO(s) is also called ferrous oxide
Fe2O3(s) is also called ferric oxide
Chemistry 20 – Unit 3 Page 7 Overhead Notes
Elements, Compounds and Nomenclature

Hydrated Compounds
some compounds have a strange-looking formula
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which has water added at the end, such as
CuSO4⋅ 5 H2O(s)
these are still ionic compounds and exist as solids
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at room temperature
the only thing we have to do is to state how many
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waters are involved
so, for CuSO4 ⋅ 5 H2O(s) , the first part is named as
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copper (II) sulfate and then we add that there are
5 waters
the Latin prefix for 5 is penta and water is called
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hydrate
the name becomes copper (II) sulfate pentahydrate
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Number Latin Prefix Number Latin Prefix
1 Mono 6 hexa
2 Di 7 hepta
3 Tri 8 octa
4 Tetra 9 nona
5 Penta 10 deca
Chemistry 20 – Unit 3 Page 8 Overhead Notes
Elements, Compounds and Nomenclature

Naming Molecular Compounds
molecular compounds are formed by combining
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nonmetallic elements
when these elements are combined they may form
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more than one compound
carbon and oxygen may combine to form CO(g) or
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CO2(g)
nitrogen and oxygen may combine to form NO(g) or
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NO2(g) or N2O4(g)
note that subscripts are not simplified and another
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naming system is used
Example
CO2(g) is made from carbon and oxygen
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the first element gets the normal name
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the second element gets and “ide” ending
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now we must state how many of each element
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is being used by inserting prefixes before
each element name
there is one carbon (monocarbon) and two
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oxygens (dioxide)
if the first element is a “mono” the prefix is
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ignored but is used for the second element
NO(g) is nitrogen monoxide
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NO2(g) is nitrogen dioxide
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N2O4(g) is dinitrogen tetroxide
•
Chemistry 20 – Unit 3 Page 9 Overhead Notes
Elements, Compounds and Nomenclature

there is no general rule for determining states of
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matter
each molecular compound has its own
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characteristic state of matter at room temperature
and these are learned as you go along
some molecular compounds have classical names
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that have no logic involved in their naming system
these we just memorize
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Examples
H2O(l) is water
NH3(g) is ammonia
O3(g) is ozone
CH4(g) is methane
C6H12O6(s) is glucose
C12H22O11(s) is sucrose
CH3OH(g) is methanol
C2H5OH(l) is ethanol
H2O2(l) is hydrogen peroxide
H2S(g) is hydrogen sulfide
Chemistry 20 – Unit 3 Page 10 Overhead Notes
Elements, Compounds and Nomenclature

Hydrogen Compounds
hydrogen compounds are those which contain a
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hydrogen at the beginning of the chemical
formula and are dissolved in water (aqueous)
• Examples: HCl (g) , HNO 3(aq)
hydrogen bonds covalently (shares electrons) to
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nonmetals to form a molecular compound
which may be any state of matter, depending on
the species being formed
most hydrogen compounds are named as acids
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the only exceptions to this rule are the following
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pure substances
• HCl (g) – hydrogen chloride
• H2S(g) – hydrogen sulfide
• HCN (g) – hydrogen cyanide
when hydrogen compounds dissolve in water
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they form acidic solutions
• HCl (g) is bubbled into water to form a solution
called hydrochloric acid
Chemistry 20 – Unit 3 Page 11 Overhead Notes
Elements, Compounds and Nomenclature

Properties of Acids
1. turns litmus indicator red
• tastes sour
• neutralizes bases
• conducts an electrical current
• pH is lower than 7
Naming Acids
Naming acids is easy if we follow this table:
hydrogen ___ide becomes hydro___ic acid
hydrogen ___ate becomes ________ic acid
hydrogen ___ite becomes ________ous acid
Examples: Name the following acids.
HF(aq) – the normal name given to this chemical is
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hydrogen fluoride, therefore, hydrogen fluoride
becomes hydrofluoric acid
HNO3(aq) – the normal name given to this chemical
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is hydrogen nitrate, therefore, hydrogen nitrate
becomes nitric acid
HNO2(aq) – the normal name given to this chemical
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is hydrogen nitrite, therefore, hydrogen nitrite
becomes nitrous acid
We can read the table backwards to write out the
chemical formula of a given acid name.
Chemistry 20 – Unit 3 Page 12 Overhead Notes
Elements, Compounds and Nomenclature

Example: Give the chemical formula for
hydrosilicic acid.
the acid name came from hydrogen silicate,
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therefore the formula must be H2SiO3(s)
now change states to give the acid formula,
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H2SiO3(aq)
Classification of Acids
Binary Acids: contain a hydrogen and one other
kind of atom
Example: HCl(aq)
Oxo Acids: contain a hydrogen, an oxygen and one
other kind of atom
Example: HNO3(aq)
Chemistry 20 – Unit 3 Page 13 Overhead Notes
Elements, Compounds and Nomenclature