Naming Compounds and Writing Formulas

1
Naming Compounds and Writing Formulas

• By Ms. Buroker

2
The Significance of Chemical Formulas

• A chemical formula communicates two things the
  types of elements and the number of atoms that
  make the chemical compound.
• 1.) Formula Units Ionic Compounds
• Ex NaCl, MgCl2
• 2.) Molecular Formulas Covalent compounds
• Ex CO2, H2O

3
Binary Ionic Compounds

• Binary Ionic Compounds contain one type of metal
  and one type of non-metal.
• To Name Them
• STEP 1 Name the first ion (cation)
• If the first ion is a transition element other
  than zinc, cadmium, or silver, you must use a
  Roman Numeral with the name well discuss this
  later.
• STEP 2 Name the second ion (anion) and change
  the suffix to ide.

4
Examples Binary Ionic NaCl
Name the metal ion
Sodium
Chloride
Name the nonmetal ion, changing the suffix to
ide.
CaO
Calcium
Oxide
Al2S3
Aluminum
Sulfide
MgI2
Magnesium
Iodide
5
What about the transition metals and using
roman numerals? How does that work? Lets see.
Notice metal and nonmetal.
FeO
Name the first ion. Since the first ion is a
transition element, you must use a Roman Numeral
to represent the charge.
Iron
II
Oxide
How do you know the charge? Deductive reasoning.
All compounds are neutral. Oxygen has a -2 charge
(group 6A) Therefore .. Iron must have a 2
charge since there is one iron and one oxygen.
Iron gets a Roman Numeral II.
6
Name the first ion. Since it is a transition
metal, you must use a Roman Numeral. Which Roman
Numeral? The Roman Numeral is the same as the
charge of the ion. How do you find the
charge? Deductive reasoning! All compounds are
neutral Sulfur has a -2 charge (group 6A) There
are two coppers. Therefore each copper must have
a 1 charge for all ions to be neutral
Cu2S
Copper
I
Sulfide
7
Another Example MnO2
Name the first ion. Since it is a transition
metal, you must use a Roman Numeral. How do you
determine the Roman Numeral? It is the same as
the charge. What is the charge of Mn? All
compounds are neutral. Oxygen (group 16) has a -2
charge. There are two oxygens and one
Mn. Therefore Mn must have a 4 charge for this
compound to be neutral.
Manganese
IV
oxide
8
So why must we use Roman Numerals with transition
elements?
The metals in groups 1A, 2A, and 3A have single,
definite charges. Group 1A metals have a 1
charge. Group 2A metals have a 2 charge. Group
3A metals have a 3 charge. Transition metals may
have multiple charges usually two different
positive charges. For example, there are two
copper oxide compounds
Cu2O and CuO
Cu2O Copper I oxide Copper is 1
CuO Copper II oxide Copper is 2
We cant just say Copper oxide. Which one of
these is Copper oxide? We must distinguish these
by using a Roman Numeral
9
There are three transition elements which do not
require a Roman Numeral because they have single
definite charges. Zinc Zn2 Cadmium
Cd2 Silver Ag1
You need to remember the charges for these!!!
No Roman Numerals needed for these.
Ag2O
Name the first ion.
Name the second ion changing the suffix to ide.
Silver
oxide
ZnCl2
Name the first ion.
Name the second ion changing the suffix to ide.
Zinc
chloride
10
Sometimes you will see the transition elements
named using common names. Transition metals named
with Roman Numerals involves stock names.

• The common names use the Latin derivative of the
  elements name with a suffix of either ous or
  ic.
• The ous suffix name corresponds with the
  smaller charge.
• The ic suffix name corresponds with the larger
  charge.

11
In Summary
Stock name Common Name
Copper I Cuprous
Copper II Cupric
Iron II Ferrous
Iron III Ferric
Lead (II) Plumbous
Lead (IV) plumbic
12

• How do you write formulas for binary ionic
  compounds given the name?
• Two simple steps
• Write the symbol and charge of each ion
• Balance the charges by providing subscripts

Magnesium chloride
Write the symbol and charge of each ion.
Balance the charges by supplying subscripts.
Subscripts tell how many of each atom is present.
Mg2 Cl-1
Cl-1
MgCl2
You need a second Cl-1 to balance the charges
13
More examples Iron III bromide
Write the symbol and charge of each ion. The
charge of the iron is provided by the Roman
Numeral.
Fe3 Br -1
Br -1
Br -1
Balance the charges by supplying subscripts. The
subscripts tell how many of each ion is needed to
balance the compound.
FeBr3
Youll need three bromine ions to balance the one
iron.
14
Write the symbol and charge of each ion.
Balance the charges by supplying subscripts.
In this case the charges do not evenly divide
into each other. You must find the least common
multiple. SIX
Aluminum Sulfide
Al3 S-2
S-2
Al3
S-2
How many aluminums are needed to arrive at a 6
charge?
2
Al2S3
How many sulfurs are needed to arrive at a -6
charge?
3
15
Naming Ternary Compounds

• These compounds contain at least one polyatomic
  ion.
• What is a polyatomic ion?
• Lets look at the name to try to understand.
• It is an ion that means it has a charge.
• It is polyatomic that means it is made of more
  than one atom.
• Lets look at some examples of polyatomic ions

16
This ion is composed of one carbon and three
oxygens and the entire group has a charge of -2.
CO3-2 Carbonate
Polyatomic ion Group of atoms that act as a
unit and carry a charge. More examples
CN- Cyanide
MnO4-2
Permanganate
SO4-2
Sulfate
Phosphate
PO4-3
C2H3O2-1
Acetate
SO3-2
Sulfite
OH-1
Hydroxide
ClO4-1
Perchlorate
NO3-1
Nitrate
ClO3-1
Chlorate
NO2-1
Nitrite
ClO2-1
Chlorite
NH41
Ammonium
ClO-1
Hypochlorite
You need to learn these!!!
17
How do you recognize Ternary Ionic Compounds?

• Composed of two ions in which at least one is a
  polyatomic ion.
• There is only one positive polyatomic ion that
  you need to memorize (NH41)

18
How do you name Ternary Ionic
Compounds? EASY! PIECE OF CAKE! NO
PROBLEM! Name the first ion. Name the second
ion. Examples
When you look at this compound you should
recognize that this is NOT binary. There are
THREE elements present. When you see this,
immediately look for a polyatomic ion. Carbonate
is present here.
Na2CO3
Sodium
carbonate
Notice that you do NOT change the suffix just
name the polyatomic ion
Name the first ion.
Name the second ion.
19
A few more examples Fe(OH)3
Name the first ion.
Iron
Remember that iron requires a Roman Numeral since
it is a transition element. What Roman Numeral
should be used?
III
hydroxide
Since there are 3 OH groups, each with a -1
charge, the charge of the iron must be 3 for the
compound to be neutral

• The Roman Numeral comes from the charge of the
  ion. How do you find the charge of the iron?
• You know two things
• All compounds are neutral.
• You know the charge of OH (-1)

Name the polyatomic ion.
20
Name the first ion.
NH4Cl
Name the second ion.
Ammonium
chloride
Notice that since the second ion is a nonmetal
that, like binary ionic compounds, the suffix of
the nonmetal changes to ide.
Name the first ion.
(NH4)3PO4
Name the second ion.
Ammonium
phosphate
21
ONE more example Cu2SO4
Name the first ion.
You should realize that you need a Roman Numeral
since copper is a transition metal.
sulfate
Copper
I
The Roman Numeral is the same as the charge. What
is the charge? The charge of sulfate is -2. Since
there are two coppers, the charge of the copper
must be 1.
Name the second ion.
22

• How do you write formulas for Ternary Ionic
  Compounds?
• Very much like writing formulas for Binary Ionic
  Compounds.
• Two steps
• 1.) Write the formulas/symbols of each ion.
• 2.) Balance the charges by supplying subscripts.
• If a subscript is needed for a polyatomic ion, it
  must be put in parentheses with the subscript on
  the outside.

23
Aluminum nitrate
First, you can tell from the name that there is a
polyatomic ion present (nitrate). All binary
ionic compounds have suffixes of ide.
Al3 NO3-1
Al(NO3)3
Write the formula/symbol and charge of each ion.
Balance the charges by supplying
subscripts. Since Al is 3 and NO3 is -1, you
need a total of 3NO3-1 to balance one Al3 Since
you will need a subscript of 3 for NO3-1, you
need to put this in parentheses with the 3
outside.
24
Lead (IV) acetate
Write the formula/symbol and charge of each ion.
Pb4 C2H3O2-1
Balance the charges by supplying subscripts.
Since Pb is 4 and C2H3O2 is -1, you will need 4
C2H3O2-1 to balance 1Pb4
Pb(C2H3O2)4
Write the formula/symbol and charge of each ion.
Calcium phosphate
Ca2 PO4-3
Balance the charges by supplying subscripts.
Since Ca is 2 and PO4 is -3, you will need 3
Ca2 to balance 2 PO4-3
Ca3(PO4)2
25
Naming Binary Molecular Compounds

• These compounds consist of two non-metals and
  to name them, you need to know the following
  prefixes

1 Mono-
2 Di-
3 Tri-
4 Tetra-
5 Penta-
6 Hexa-
7 Hepta-
8 Octa-
9 Nona-
10 Deca-
26
The Rules.

• The first nonmetal only gets a numeric prefix
  when there is more than one. No prefix if there
  is only one.
• The second element always gets a numeric prefix
  and always has a suffix of -ide

27
CO2 Carbon dioxide CO Carbon
monoxide N2O4 Dinitrogen tetraoxide H2O Dihydrogen
monoxide CCl4 Carbon tetrachloride
Name the first element. Since there is only one,
no prefix is needed. The second element always
gets a prefix and a suffix of ide.
Name the first element. Since there are two
present, the prefix di is needed. The second
element always gets a prefix and a suffix of ide.
28
Writing Formulas for Binary Molecular Compounds

• Very easy to do!!! The prefixes tell you how to
  write the formulas. DO NOT CONSIDER CHARGES.
  NONMETALS ARE ALL NEGATIVE SO TO USE CHARGES DOES
  NOT WORK!

29
Silicon and oxygen are both nonmetals. The lack
of a prefix on silicon means that there is only
ONE silicon. The prefix di in front of oxide
means that there are TWO oxygens.
Silicon dioxide
SiO2
Diphosphorous pentachloride
Phosphorous and chloride are both nonmetals. The
prefix di means that there are TWO
phosphorouses (Is that a word?) The prefix
penta before chlorine means that there are five
chlorines.
P2Cl5
30
Nitrogen and oxygen are both nonmetals. The lack
of a prefix on nitrogen means only ONE
nitrogen. The prefix mono on oxygen indicates
ONE oxygen.
Nitrogen monoxide
NO
Is this not sooooooo easy!??
31
Naming Binary Acids

• First of all, what is a binary acid?
• Binary Acids are those which contain hydrogen
  and a non-metal.

32
Stem or root of nonmetal
Prefix
Suffix
-ic
Acid
lt NM gt
Hydro-
HCl is a binary acid hydrogen - nonmetal
HCl
Hydro
chlor
ic
Acid
Hydro
iod
ic
Acid
HI
Hydro
sulfur
ic
Acid
H2S
33
Writing Formulas For Binary Acids

• The obvious pattern of the name tells you that it
  is a binary acid. HydroltNMgtic Acid.
• Therefore, you know that the acids begins with
  hydrogen and contains a nonmetal which you can
  identify between the Hydro and the ic
• To arrive at the formula, you pretend that
  hydrogen is 1 and using the normal charge of the
  nonmetal, balance the formula by supplying
  subscripts.

34
Hydrophosphoric acid
The name tells you that it is definitely a binary
acid.
H1 P-3
H3P
Remember that the P has a -3 charge because it is
in group 5A
35
Lets Practice Ca(OH)2 Calcium hydroxide SO2 Sulfu
r dioxide (NH4)3PO4 Ammonium phosphate Co2(CO3)3 C
obalt (III) carbonate HBr Hydrobromic acid
Ternary Ionic
Binary molecular
Ternary Ionic
Ternary Ionic
Binary acid
36
Potassium acetate KC2H3O2 Cadmium
nitrate Cd(NO3)2 Aluminum oxide Al2O3 Hydrosulfuri
c acid H2S Difluorine trioxide F2O3
Ternary Ionic
Ternary Ionic
Binary Ionic
Binary acid
Binary molecular
37
Naming Ternary Acids

• These compounds begin with hydrogen since they
  are acids.
• Attached to the hydrogen is a polyatomic ion
• Hydrogen polyatomic ion

38
How are Ternary Acids named? There are two
categories of naming depending on the suffix of
the polyatomic ion. First Category If the
polyatomic ion has a suffix of ate or ide, use
the following pattern
suffix
-ic
acid
ltRoot of polyatomic iongt
Ternary Acid contains the polyatomic ion
chlorate (suffix ate)
Ternary Acid contains the polyatomic ion
nitrate (suffix ate).
Ternary Acid contains the polyatomic ion
sulfate (suffix ate).
Ternary Acid contains the polyatomic ion
cyanide (suffix ide).
HClO3
Chlor
ic
Acid
Nitr
ic
Acid
HNO3
Sulfur
ic
Acid
H2SO4
Acid
ic
HCN
hydrocyan
39
Second Category If the polyatomic ion has a
suffix of ite, use the following pattern
suffix
-ous
acid
ltRoot of polyatomic iongt
Ternary acid contains polyatomic ion, nitrite
(-ite suffix).
HNO2
acid
Nitr
ous
Chlor
ous
acid
Ternary acid contains polyatomic ion, chlorite
(-ite suffix).
HClO2
Ternary acid contains polyatomic ion, sulfite
(-ite suffix).
Sulfur
ous
acid
H2SO3
40
Writing Formulas for Ternary Acids First, a
ternary acid is easy to distinguish from a binary
acid. ALL binary acids have the prefix hydro-.
NO Ternary acids have the prefix hydro-.
Acetic acid
This is an acid, but NOT a binary acid. This is a
ternary acid. The -ic suffix in the acid name
tells you that the polyatomic ion must have a
-ate suffix acetate. To write the formula,
pretend that hydrogen is 1 and balance the
charges.
H1 C2H3O2-1
HC2H3O2
41
Hypochlorous acid
This is a Ternary acid (does not begin with
hydro-.
H1 ClO-1
The -ous suffix indicates that the polyatomic
ion in this acid has a suffix of -ite -
hypochlorite
HClO
Pretend that hydrogen is 1 and balance the
charges.
This is a Ternary acid (does not begin with
hydro-.
Phosphoric acid
H3PO4
The -ic suffix indicates that the polyatomic
ion in this acid has a suffix of -ate -
phosphate
Pretend that hydrogen is 1 and balance the
charges.