Chapter 9
Chemical Names
and Formulas
Section 9.1 – Naming Ions

Objectives:
 Identify
the charges on monatomic ions by
using the periodic table and name the ions
 Define a polyatomic ion and write the
names and formulas of the most common
polyatomic ions
 Identify the two common endings for the
names of most polyatomic ions
1st let’s review…Atoms and Ions

Atoms are electrically neutral

Ions are atoms, or groups of atoms, with a
charge (positive or negative)
 there
is the same number of protons and electrons
 there
is a different numbers of protons and
electrons.

Only electrons can move

Ions are made by gaining or losing electrons.
Anions

A negative ion
 Gained electrons
 Nonmetals can gain electrons.
 Charge is written as a superscript on the
right.
F
1
O
-
2
Has gained one electron
(-ide is new ending = fluoride)
Gained two electrons (oxide)
Cations

A positive ion
 Formed
by losing electrons
 More protons than electrons
 Metals can lose electrons
K1+
has lost one electron
(no name change for positive ions)
Ca2+
has lost 2 electrons (calcium ion)
Oxidation States


During this chapter we will be referring to “oxidation
states”.
Later in the year we will deal with oxidation states in
more detail. For now we will just look at some of the
basic rules about oxidation numbers.

The periodic table included in
your reference tables give
selected possible oxidation
states of each element.
Oxidation States

A neutral atom with no charge has an
oxidation state of zero.
 An

A monatomic ion has an oxidation state equal
to its charge.
 O2-

atom of C has an oxidation state of zero.
has an oxidation state of -2
So for now, while we are talking about ions,
oxidation states and charge will seem like the
same thing, but later we will build on our
understanding of oxidation states.
Oxidation States & Ionic Charges




The periodic table included in your reference tables
give selected possible oxidation states of each
element.
However, we are talking now ONLY about ions. Atoms
that are part of a compound have oxidation states as
well.
When we predict what type of ions an atom will form
we will follow a set of rules, and not all the oxidation
states listed in the periodic table will apply.
Example: +4 is an oxidation state listed
for C, however, we wont see:
C4+
Predicting Ionic Charges


We will now describe the guidelines for
predicting ionic charges. The guidelines
predict the type of ions that will almost always
form.
A few points:
 Names
of ions are given in the slides before an
explanation of the naming system so that you can
refer back to them when you look at your notes.
Don’t worry if you don’t understand the naming
initially.
 Don’t get caught up in the exceptions.
Predicting Ionic Charges
Group 1: Lose 1 electron to form 1+ ions
H1+
Li1+
Na1+
K1+
Rb1+
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
Predicting Ionic Charges
Neither! Group 14
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
Cl1-
Chloride
I1-
Iodide
Br1-
Bromide
Group 17: Gains
1 electron to form
1- ions
Predicting Ionic Charges
Group 18: Stable
noble gases do not
form ions!
Predicting Ionic Charges
Many transition elements will form more than
one type of ion.
2+
Iron
(II)
=
Fe
Note the use of Roman
3+
Iron
(III)
=
Fe
numerals to show charges
Predicting Ionic Charges
Some of the post-transition elements also
have more than one possible oxidation state.
Tin (II) = Sn2+
Lead (II) = Pb2+
Tin (IV) = Sn4+
Lead (IV) = Pb 4+
Predicting Ionic Charges
Some transition elements have only one possible
oxidation state, such as these three that are
always:
Silver = Ag1+
Zinc =
Zn2+
Cadmium = Cd2+
Naming Cations

Two methods can clarify when more
than one charge is possible
 Stock
System – uses roman numerals in
parenthesis to indicate the numerical value
 Classical Method – uses root word with
suffixes (-ous, -ic)

Does not give true value
Using the Stock System for Cations:

If the charge is always the same just write the
name of the metal. NO roman numerals. Use for:
 representative
elements
 transition metals that have only one ionic charge



Silver is always 1+ (Ag1+)
Cadmium and Zinc are always 2+ (Cd2+ and Zn2+)
If ions of different charges can form, indicate
their charge with roman numerals in parenthesis
after the name of the metal. Use for:
 Transition
metals can have more than one type of
charge
Review this tonight for HW
 Table 9.2 pg. 255 lists a number of ions and their
names
Practice by naming these:
Na1+
 Ca2+
 Al3+
 Fe3+
 Fe2+
 Pb2+
 Li1+

Sodium ion
Calcium ion
Aluminum ion
Iron (III)
Iron (II)
Lead (II)
Lithium ion
Write Formulas for these:
Potassium ion
 Magnesium ion
 Copper (II) ion
 Chromium (VI) ion
 Barium ion
 Mercury (II) ion

K1+
Mg2+
Cu2+
Cr6+
Ba2+
Hg2+
Naming Anions
Anions are named the same regardless
of the charge
 Stem of the element name+ “ide”
 F 1- a flourine atom becomes a flouride
ion

Practice by naming these:

Cl1- Chloride ion

N3- Nitride ion

Br1- Bromide ion

O2- Oxide ion

Ga3+ Gallium ion
Write Symbols for these:
Sulfide ion
 Iodide ion
 Phosphide ion
 Strontium ion

S2I1P3Sr2+
Polyatomic ions








Groups of atoms that stay together and have
an overall charge, and one name
Usually end in –ate or -ite
Acetate: C2H3O21-
Nitrate: NO31Nitrite: NO21Permanganate: MnO41Hydroxide: OH1Cyanide: CN1-
Note Table 9.3 on page 257







Sulfate: SO4
Sulfite: SO32Carbonate: CO32Chromate: CrO42Dichromate: Cr2O72Phosphate: PO43Phosphite: PO332-
Ammonium: NH41+
If the polyatomic ion
begins with H, then
combine the word
hydrogen with the other
polyatomic ion present:
H1+ + CO32- → HCO31hydrogen + carbonate →
hydrogen carbonate ion
(One of the few
positive polyatomic ions)
9.2
Section 9.2 – Naming and Writing
Formulas for Ionic Compounds

Objectives:
 Apply
the rules for naming and writing
formulas for binary ionic compounds
 Apply the rules for naming and writing
formulas for compounds with polyatomic
ions
Binary Compounds


Compound composed of 2 elements
Can be either ionic or molecular
In This Section, 9.2…
 We will look only at Binary Ionic Cmpds
(Next section covers Binary Molecular Cmpds)
 1st we will look at how to name a binary
compound when we are given the formula unit
 2nd we will look at how to determine the
formula unit when given the name of the
compound
Naming Binary Ionic Compounds


Place the name of the cation first
Followed by the name of the anion
Simple Example: Cs20
 We know that Cs forms +1 ions
 The
Rule (from 9.1): Cations with one possible
charge have the name of the element

We know that O forms -2 ions
 The
Rule (from 9.1): Anions with one possible
charge have the stem of the element name +
“ide”
cesium oxide
Naming Binary Ionic Compounds


Place the name of the cation first
Followed by the name of the anion
Another Simple Example: NaBr
 We know that Na forms +1 ions
 The
Rule (from 9.1): Cations with one possible
charge have the name of the element

We know that Br forms -1 ions
 The
Rule (from 9.1): Anions with one possible
charge have the stem of the element name +
“ide”
sodium bromide
Naming Binary Ionic Compounds
Metals with multiple oxidation states.
 Some metals can form ions with more
than one charge (usually transition
elements)
 Use
a roman numeral in their name
 PbCl2 – use the anion to find the charge on
the cation (chloride is always 1-)
Pb2+ is lead(II) cation
 PbCl2 = lead(II) chloride

Naming Binary Ionic Compounds

Example involving metal with multiple ions: CuO

Why?
 Because


Copper forms 2 different ions
Copper I & Copper II
Which one is it?
 Work
backwards…start with Oxygen
Oxide always has a 2- charge
 remember ionic compounds are always electrically
neutral
 Copper must have a 2+ charge to balance the 2charge
 The compound must be copper(II) oxide

Naming Binary Ionic Compounds


Try another… SnF2
What ions does Sn form?
 Tin
(II) = Sn2+
 Tin (IV) = Sn4+

What ions does Flourine form?
F
always has a charge of 1 There are two F ions  2 Therefore the charge of tin must be 2+ to balance
the 2- charge of flourine (F2)

The name of SnF2 is tin(II) flouride


We just named Binary Ionic Compounds
based on the formula unit.
Now we will be given the name. From
the name we will determine the formula
unit.
Writing Ionic Compound Formulas
Steps to Follow:
 Write the element symbols of the cation and
anion including charges
 Check to see if the charges are balanced
 Positive
charge must balance the negative charge
so the net charge of the compound is zero

Add subscripts to balance the charges using
the criss-cross method
Writing Ionic Compound Formulas

Example: Iron (III) chloride
1. Write the element symbols
for the cation and anion,
including CHARGES!
2. Check to see if charges are
balanced.
3. Balance charges , if necessary,
using subscripts.
Use the criss-cross method to
balance the subscripts.
Fe3+ Cl-
3
Now balanced.
Not balanced!
= FeCl3
Writing Ionic Compound Formulas
Example: Aluminum sulfide
1. Write the symbols for the
cation and anion, including
CHARGES!
2. Check to see if charges
are balanced.
3. Balance charges , if
necessary, using subscripts.
Use the criss-cross method to
balance the subscripts.
3+
Al
2
2S
3
Now balanced.
Not balanced!
= Al2S3

Now let’s do a few examples that
involve polyatomic ions.
Writing Ionic Compound Formulas
Example: Magnesium carbonate
1. Write the formulas for the
cation and anion, including
CHARGES!
2. Check to see if charges
are balanced.
Mg2+ CO32They are balanced!
= MgCO3
Writing Ionic Compound Formulas
Example: Aluminum phosphate
1. Write the formulas for the
cation and anion, including
CHARGES!
3+
Al
2. Check to see if charges are
balanced.
They ARE balanced!
PO4
3-
= AlPO4
Writing Ionic Compound Formulas
Example: Barium nitrate
1. Write the formulas for the
cation and anion, including
CHARGES!
2+
Ba (
2. Check to see if charges are
balanced.
3. Balance charges , if necessary,
using subscripts. Use parentheses if
you need more than one of a
polyatomic ion. Use the criss-cross
method to balance subscripts.
NO3
-)
Now balanced.
Not balanced!
= Ba(NO3)2
2
Writing Ionic Compound Formulas
Example: Zinc hydroxide
1. Write the formulas for the
cation and anion, including
CHARGES!
2+
Zn (
2. Check to see if charges are
balanced.
3. Balance charges , if necessary,
using subscripts. Use parentheses if
you need more than one of a
polyatomic ion. Use the criss-cross
method to balance the subscripts.
OH )
Now balanced.
Not balanced!
= Zn(OH)2
2
Writing Ionic Compound Formulas
Example: Ammonium sulfate
1. Write the formula for the
cation and anion, including
CHARGES!
( NH4+) SO422
2. Check to see if charges
Now balanced.
are balanced.
Not balanced!
3. Balance charges , if necessary,
= (NH4)2SO4
using subscripts. Use parentheses if
you need more than one of a
polyatomic ion. Use the criss-cross
method to balance the subscripts.
Things to look for
If the cation name has ( ), the number
in parenthesis is the charge
 If anions end in –ide it is from the
periodic table
 If anion ends in –ate or –ite, then it is a
polyatomic ion

 Reference
table E
Sodium Chloride
Copper (II) Sulfate
Ammonium Sulfide
Barium
Cu1+ or Cu2+
What’s the
charge on SO ?
4
Oxide
Lithium Flouride
Tin (IV) Nitrate
Potassium Nitride
Mercury (II) Bromide
Calcium
Iodide
Magnesium Phosphate
Sn2+ or Sn4+
What’s the
charge on NO ?
3
How
NO2+
Hg1+many
or Hg
3
ions?
What’s the
charge on Br?
How many Br
ions?
Charges
Formula
Fe3+O2-
Fe2O3
Cr3+ (CO3)2-
Cr2(CO3)3
Ca2+ S2-
CaS
Pb2+ As3-
Pb3As2
(NH4)1+(NO3)1- (NH4)(NO3)
K1+ (C2O4)2-
K2(C2O4)
Al3+ (C2H3O2)1- Al (C2H3O2)3
Cs1+ (S2O3)2-
Cs2(S2O3)
Sr2+ P3-
Sr3P2
Sn4+ O2-
Sn2O4
Remember, for any neutral compound, the sum
of the oxidation numbers of the atoms in the
compound must equal 0.
Ba+2
+2
-1
Ba Cl2
(1 )(+2) + (2)(-1) = 0
Ba
Cl
Remember, for any neutral compound, the sum
of the oxidation numbers of the atoms in the
compound must equal 0.
Pb+4
+?
-2
Pb O2
(1 )(+?) + (2)(-2) = 0
+? + (-4) = 0
+? = +4
We don’t know if it is:
Pb(II) or Pb(IV)
Remember, for any neutral compound, the sum
of the oxidation numbers of the atoms in the
compound must equal 0.
Cr3+2
+?
-3
Cr3 (PO4)2
(3 )(+?) + (2)(-3) = 0
(3)(+?) + (-6) = 0
(3)(+?) = +6
+? = +6/3 = +2
Phosphate is always -3, but
Cr does NOT always have
the same charge.
NOW…
1.
2.
Go back to your
fix your errors.
Check your answers to:
9.3
Section 9.3 – Naming and Writing
Formulas for Molecular Compounds

Objectives:
 Interpret
the prefixes in names of
molecular compounds in terms of their
chemical formulas
 Apply the rules for naming and writing
formulas for binary molecular compounds
Molecular Compounds
Made of just nonmetals
 Smallest piece is a molecule

 Are
not be held together because of
opposite charges
 Can not use charges to figure out how many
of each atom
Molecular Compounds

EASIER!!
 Ionic
compounds use charges to determine
how many of each element is present
Have to figure out charges
 May need to criss-cross numbers

 Molecular
compounds – the name tells you
the number of atoms
 Uses prefixes to tell you the exact number
of each element present
Prefixes (table 9.4 pg. 269)
1 = mono2 = di3 = tri4 = tetra5 = penta6 = hexa7 = hepta8 = octa9 = nona10 = deca-

Again, first we will look at how to name
the compound when given the formula.
(only molecular compounds have molecular formulas, not formula units)

Then we will look at how to determine
the molecular formula based on the
name.
Naming Molecular Compounds

To write the name - write two words:
Word 1

Word 2
Prefix + name prefix + name + “– ide”
 One
exception – we do not write the
prefix mono-if there is only one of the
first element

Normally do not have the following
double vowels: “oa” “oo”
Practice by naming these:

N2O
Dinitrogen oxide

NO2
Nitrogen dioxide

Cl2O7 Dichlorine heptoxide

CBr4
Carbon tetrabromide

CO2
Carbon dioxide

BaCl2 Barium chloride
(laughing gas)
(notice no prefix
-this is ionic!)
Write Formulas for these:

diphosphorus pentoxide P2O5

tetraiodine nonoxide
I4O9

sulfur hexafluoride
SF6

dinitrogen trioxide
N2O3

carbon tetrahydride
CH4

phosphorus trifluoride PF3

aluminum chloride
AlCl3
metal and nonmeta
= ionic
Calcium Phosphate
Lead (IV) Iodide
Aluminum Hydrogen Sulfate
Iron (III) Hydroxide
Carbon Tetraiodide
Cesium Sulfate
Lithium Hydrogen Carbonate
Barium Sulfate
Aluminum Phosphide
Ammonium Nitrate
Copper (I) Oxide
Mercury (I) Carbonate
Silver Oxalate
Copper (II) Thiocyanate
Lithium Hydroxide
Silver Sulfide
Rubidium Nitride
Iron (II) Sulfate
Zinc Bromide
Lead (IV) Chromate
Manganese (II) dichromate
Strontium Hydride
Strontium Acetate
Carbon disulfide
Manganese (IV) Oxide
Potassium Phosphide
Sodium Thiosulfate
Barium Sulfide
Phosphorous Acid
Francium Permanganate
Potassium Chloride
Magnesium Iodide
Sodium Hydrogen Sulfate
Mercury (II) Phosphate
Nickel (II) Chlorate
Cadmium Flouride
Tin (II) Sulfide
Carbon Dioxide
Sodium Chloride
Antimony (III) Nitrate
Tin (IV) Carbonate
Potassium Hydrogen Sulfate
Arsenic Triodide
Ammonium Hydroxide
Silicon Tetrachloride
Ammonium Chlorate
Chromium (III) Oxalate
Nickel (II) Flouride
Sulfur Dioxide
Bismuth (II) Carbonate
Diarsenic Pentoxide
Cadmium Oxide
Ammonium Dichromate
Potassium Chlorate
Sulfur Trioxide
Zinc Nitrate
Tricarbon Tetraphosphide
Tin (IV) Oxide
Ammonium Bromide
Sodium Oxide
9.4
Section 9.4 – Naming and Writing
Formulas for Acids and Bases

Objectives
 Apply
the three rules for naming acids
 Apply the three rules in reverse to write
formulas of acids
 Apply the rules for naming bases
Acids



Acids are compounds that produce
hydrogen ions when dissolved in water
H+
Acids are compounds with 1 or more
hydrogen atoms
Acids are a group of ionic compounds
with unique properties
Chemical Formula of Acids

In general the chemical formula of an
acid is HnX
 Where
X is a monatomic or polyatomic anion
 n is a subscript indicating the number of
hydrogen ions that are combined to make
the molecule electrically neutral

The anion determines the name
Rules for Naming Acids
For acids with monatomic anions attached to
hydrogen:
• put the prefix hydro- and
• Add the ending –ic acid (instead of –ide)


HCl – hydrogen ion and chloride ion = hydrochloric acid
H2S – hydrogen ion and sulfide ion = hydrosulfuric acid
Rules for Naming Acids

If the anion has oxygen in it, then it ends in –ite or
–ate and is a polyatomic ion
If anion name ends in –ite:


Change the suffix –ite to –ous acid
use no prefix

HNO2 hydrogen and nitrite ion = nitrous acid
If anion name ends in –ate:

Change the suffix –ate to –ic acid (use no prefix)

HNO3 hydrogen and nitrate ions = Nitric acid
Naming Acids
Normal Ion Ending
Acid Name
_________-ide
Hydro-______-ic acid
_________-ate
________-ic acid
_________-ite
_________-ous acid
Practice by naming these:

HF
Hydrofluoric Acid
(Note: out of solution, HF is Hydrogen Fluoride,
but when dissolved in water it forms an acid.)

H 3P
Hydrophosphoric Acid

H2SO4
Sulfuric Acid

H2SO3
Sulfurous Acid

HCN
Hydrocyanic Acid

H2CrO4
Chromic Acid
Writing Formulas for Acids

Use the three rules for writing the
names of acids in reverse
 Hydrogen
will be listed first
 The name will tell you the anion
 Be sure the charges cancel out
 Does it start with the prefix hydro? – then
there is no oxygen, -ide ending for anion
 Name has No “hydro”?
– ate anion comes from –ic,
-ite anion comes from –ous
Write formulas for these:

hydroiodic acid
H+I-  HI

acetic acid
H+(C2H3O2)-  H(C2H3O2)
H+(CH3COO)-  H(CH3COO)

carbonic acid
H+(CO3)2-  H2(CO3)

phosphoric acid
H+(PO4)3-  H3(PO4)

hydrobromic acid
H+Br-  HBr
Names and Formulas for Bases
A base is an ionic compound that
produces hydroxide ions (OH1-) when
dissolved in water
 Bases are named the same way as other
ionic compounds

 The
name of the cation (which is a metal) is
followed by the name of the anion (which is
hydroxide)
Names and Formulas for Bases
NaOH is sodium hydroxide
 Ca(OH)2 is calcium hydroxide
 To write the formula:

 Write
the symbol for the metal cation
 Followed by the formulas for the hydroxide
ion (OH1-)
 Then use the criss-cross method to balance
the charges
9.5
Section 9.5 – The Laws Governing
Formulas and Names

Objectives
 Define
the laws of definite proportions
 Apply the rules for naming chemical
compounds by using a flowchart
 Apply the rules for writing the formulas of
chemical compounds using a flowchart
Law of Definite Proportions

In a sample of a chemical compound, the
masses of the elements are always in
the same proportions
 Because
atoms combine in simple whole
number ratios, it follows that their
proportions by mass must always be the
same
Formula from Name
Tricarbon Tetraphosphide
Name contains prefixes
yes
no
Molecular Compound
– use the prefixes to
write the chemical
formula
C3P4
Ionic Compound –
determine charges
Name contains Roman
Numerals {iron (III) hydroxide]
No Roman numerals
[Aluminum Hydrogen Sulfate]
Use roman numerals to
determine charge on
cation, CRT periodic
table or Table E for
charge on anion
Fe+3(OH)-1
Use periodic Table or Table E to
determine charge on the cations,
anions and/or polyatomic ions.
Al+3(HSO4)-1
Balance the charges (cross
over) use parentheses for any
multiple polyatomic ions
Fe(OH)3
Al(HSO4)3
QXRY
For Naming Compounds
Is Q Hydrogen?
Compound is an Acid – use
rules for naming acids
yes
Binary -> hydro___ic acid
___ite -> _____ous acid
____ate -> ____ic acid
no
Are there more
than 2 elements?
no
Is Q a metal?
no
Compound is
Binary molecular
– use prefixes on
cation and anion
yes
Does Cation have only
one oxidation state?
no
yes
yes
Does Cation have only
one oxidation state?
yes
Name the ions
– anion
becomes -ide
no
Name the ions
but use roman
numeral with
cation to indicate
oxidation state
Name the ions
– if anion is one
element then it
becomes -ide
Helpful Reminders
1.
2.
3.
4.
5.
In an ionic compound, the net ionic charge is
zero (criss-cross method)
An –ide ending essentially indicates a binary
compound
An –ite or –ate ending meaning there is a
polyatomic ion that has oxygen
Prefixes generally mean molecular; the
prefix shows the number of each atom
A roman numeral after the cation is the
ionic charge of the cation