Transcript Nomenclature - KP's Chemistry

Nomenclature
Honors Chemistry
Mrs. Partridge
Chemical Names and Formulas

Every substance is either an element or
a compound
Chemical Names and Formulas

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In nature, only the noble gas elements
tend to exist as isolated atoms
Noble gases are monatomic – consisting
of single atoms
Chemical Names and Formulas

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A compound consists of more than one
kind of atom
A compound is either molecular or ionic
in nature
Molecules and Molecular
Compounds

A molecule is the
smallest electrically
neutral unit of a
substance that still
has the properties
of the substance
Molecules and Molecular
Compounds
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Molecules are made up of 2 or more
atoms that act as a unit
Diatomic molecules are composed of 2
atoms (O2)
Triatomic molecules are composed of 3
atoms (O3 ozone)
Molecules and Molecular
Compounds

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Atoms of different elements combine
chemically to form compounds
Compounds composed of molecules are
called molecular compounds
Molecules and Molecular
Compounds

Molecular compounds tend to have
relatively low melting and boiling points
Molecules and Molecular
Compounds
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Most molecular compounds are
composed of 2 or more nonmetals
The molecules of a given molecular
compound are all the same
Ions and Ionic Compounds
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Not all compounds are molecular. Many
compounds are composed of particles
called ions
Ions are atoms or groups of atoms that
have a positive or negative charge
Ions and Ionic Compounds
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Ions conduct electricity
Ions and Ionic Compounds
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Metals tend to form
ions by losing one or
more electrons
A cation is any atom
or group of atoms
that has a positive
charge
Ions and Ionic Compounds
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For metallic elements, the name of a
cation is the same as the name of the
element
Monatomic cation = name of the element
Ca2+ = calcium ion
Ions and Ionic Compounds

A metallic atom is
chemically different
than a metallic ion
Na atom
is highly
reactive
Ions and Ionic Compounds
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Nonmetals tend to form anions by
gaining one or more electrons
Ions and Ionic Compounds
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An anion is an atom or group of atoms
that have a negative charge
Ions and Ionic Compounds
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The name of an anion of a nonmetal is
NOT the same as the element name.
The name typically ends in –ide
Sulfur
Sulfide
Ions and Ionic Compounds
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Compounds composed of cations and
anions are called ionic compounds
Ions and Ionic Compounds
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Although they are composed of ions,
ionic compounds are electrically neutral
The TOTAL positive charge = the
TOTAL negative charge
Ions and Ionic Compounds
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Ionic compounds are usually solid
crystals at room temperature, and melt
at high temperatures
Chemical Formulas

A chemical formula shows the kinds and
numbers of atoms in the smallest
representative unit of the substance
Chemical Formulas
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If the molecule has more than one atom
of the element, a subscript is used
Cl2
subscript
Molecular Formulas
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The chemical formula of a molecular
compound is called a molecular formula
CO2
Molecular Formulas

Molecular formulas show the
composition of a molecule, NOT the
structure
Formula Units
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Chemical formulas can also be written
for ionic compounds
Formula units are used to represent an
ionic compound.
A formula unit is the lowest wholenumber ration of ions in the compound
Formula Units

Ionic charges are used in the crisscross method to derive the correct
formula, but they are not shown in the
formula
+2
Mg
-1
Cl
MgCl2
Monatomic Ions

For monatomic ions, the ionic charges
can be determine by using the periodic
table
Predicting Ionic Charges
Group 1: Lose 1 electron to form 1+ ions
H+
Li+ Na+
K+
Predicting Ionic Charges
Group 2: Loses 2 electrons to form 2+ ions
Be2+
Mg2+
Ca2+
Sr2+
Ba2+
Predicting Ionic Charges
B3+
Al3+
Ga3+
Group 13: Loses 3
electrons to form
3+ ions
Monatomic Ions
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Metallic elements tend to LOSE
electrons. Metals in group IA, 2A, and
3A lose electrons when they form
cations
Monatomic Ions

The ionic charge is positive and is
NUMERICALLY equal to the group
number
Predicting Ionic Charges
Neither! Group 13
elements rarely form
ions.
Group 14: Lose 4
electrons or gain
4 electrons?
Predicting Ionic Charges
N3- Nitride
P3- Phosphide
As3- Arsenide
Group 15: Gains 3
electrons to form
3- ions
Predicting Ionic Charges
O2- Oxide
S2- Sulfide
Se2- Selenide
Group 16: Gains 2
electrons to form
2- ions
Predicting Ionic Charges
F1- Fluoride
Br1- Bromide
Cl1-Chloride
I1- Iodide
Group 17: Gains 1
electron to form
1- ions
Monatomic Ions
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The numerical charge of an ion of a
Group A nonmetal is determined by
subtracting the group number from 8
Nonmetals tend to gain electrons and
form anions, so the sign of the charge
is negative
Predicting Ionic Charges
Group 18: Stable
Noble gases do not
form ions!
Monatomic Ions
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Noble gases do not form ions
Predicting Ionic Charges
Groups 3 - 12: Many transition elements
have more than one possible oxidation state.
Iron(II) = Fe2+
Iron(III) = Fe3+
Predicting Ionic Charges
Groups 3 - 12: Some transition elements
have only one possible oxidation state.
Zinc = Zn2+
Silver = Ag+
Monatomic Ions

Many transitional metals are capable of
forming 2 cations. There are 2 ways to
name them. The stock name uses a
Roman numeral (I, II, III) in
parentheses after the symbol
indicating the charge.
Monatomic Ions
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The classical naming system uses a root word
with different suffixes
The suffix –ous is used to name the cation
with the lower of the 2 ionic charges
Fe2+ is ferrous ion
The suffix –ic is used with the higher of the
2 ionic charges
Fe3+ is ferric ion
Polyatomic Ions

Polyatomic ions are tightly bound
groups of atoms that behave as a unit
and carry a charge
Polyatomic Ions
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MOST polyatomic ions end in –ite or-ate.
3 exceptions: ammonium ion (NH4+), cyanide
ion (CN-) and hydroxide ion (OH-)
The charge of each polyatomic ion in a given
pair is the same, but the –ite ending
indicates one less oxygen atom than the –ate
ending
NO3nitrate
NO2- nitrite
SO42- sulfate
SO32- sulfite
Writing Formulas for Binary
Ionic Compounds

Compounds composed of 2 elements are
called binary compounds
H2O
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When writing the formula for a binary
compound, the cation is ALWAYS
written first
Writing Formulas for Binary
Ionic Compounds
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The positive charge = the negative
charge. The net ionic charge must = 0.
Written using the criss-cross method,
but remember to use the LOWEST
whole number ratio of ions. Ca2+ and
S2- would criss-cross to Ca2S2, but the
lowest whole number ratio of ions
reduces to CaS
Naming Binary Ionic Compounds
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Name the compound by naming the ions
in the order written in the formula
Na+ and BrNaBr
sodium
ion
bromide
ion
sodium bromide
Naming Binary Ionic Compounds
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The name of the transition metal that
has more than one ionic charge must
include a Roman numeral (or the proper
suffix)
Fe2+ and
ClFeCl2
iron (II)
ion
Ferrous
ion
chloride
ion
chloride
ion
iron (II) chloride
ferrous chloride
Ternary Ionic Compounds
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Ternary compounds contain 3 elements
CaCO3 calcium carbonate
1
2
3
Ternary Ionic Compounds
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Write the formula for each ion in the order listed in
the name (cation followed by anion), then use the
criss-cross method to determine the subscripts. If
more than 1 polyatomic ion is needed, place the
polyatomic ion formula in parentheses, followed by a
subscript showing the number needed
Mg2+
magnesium
ion
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and
OH-
hydroxide
ion
Mg(OH)2
magnesium
hydroxide
When naming ternary ionic compounds from their
formulas, you must recognize the polyatomic ions
first
Binary Molecular Compounds
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Binary molecular compounds are
composed of 2 nonmetals
They are composed of molecules, NOT
IONS, so the criss-cross method will
NOT work
Use prefixes to tell how many atoms
are present
Binary Molecular Compounds
Prefix MonoNumber
1
Di-
Tri-
2
3
Prefix Hexa- Hepta- OctaNumber
6
7
8
Tetra- Penta4
5
Nona-
Deca-
9
10
Binary Molecular Compounds
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Always end the name in –ide
The vowel at the end of a prefix is
often dropped when the name of the
element begins with a vowel (carbon
monoxide not monooxide)
When a single atom of the FIRST
element, omit the prefix mono-
Binary Molecular Compounds
CO2
1st element one carbon,
Drop the mono and name
2nd element, two oxygens =
di, oxygen changes ending
to oxide
Carbon dioxide
Naming Common Acids
Consider acids to be combinations of
anions connected to as many hydrogen
ions (H+) as needed to make the
molecule electrically neutral
 If the acid is a binary compound:
hydro - + root name of anion + -ic acid
H2S
hydro + sulfur + ic acid =
hydrosulfuric acid

Naming Common Acids
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If the acid contains a polyatomic anion,
omit the hydro -, and change an –ate
suffix to –ic acid, or change an –ite
suffix to –ous acid
H2SO4
H2SO3
sulfuric acid
sulfurous acid