Transcript Naming Compounds and Writing Formulas

Naming Compounds and
Writing Formulas
5 types of chemical compounds
•Binary ionic -
metal ion – nonmetal ion
•Ternary ionic - at least one ion is a
polyatomic ion
•Binary molecular -
two nonmetals
•Binary acid - H – nonmetal
•Ternary acid - H – Polyatomic ion
Tips to keep in mind when naming and writing formulas:
Always keep your Periodic Table handy – You should
have it in front of you ALWAYS when you are
naming and writing formulas.
Remember that metals (except Hydrogen) are
found to the left of the stairstep on the Periodic
Table.
Nonmetals are found on the right side of the
Periodic Table.
Transition Metals are found from Group 3 to the
stairstep (except aluminum which is a regular metal)
How do you name binary ionic
compounds?
(composed of two elements – a metal and a nonmetal)
•Name the first ion
•If the first ion is a transition element other
than zinc, cadmium, or silver, you must use a
Roman Numeral with the name – we’ll
discuss this later.
•Name the second ion changing the suffix to:
–ide.
Examples
What is the name of this compound:
NaCl
HIJKLMNO?
Sodium Chloride
Name
the
metal ion
WATER – “H”
to “O”
CaO
Calcium
Oxide
Al2S3
Aluminum Sulfide
Name the nonmetal
ion, changing the
suffix to –ide.
MgI2
Magnesium Iodide
BaNa2
The should
of
this is–Banana!
This
isname
two metals
not
a binary with
ionic this
compound
You
recognize
a problem
one!
What about the transition metals and using roman
numerals? How does that work?
FeO
Iron II Oxide
Notice – metal and nonmetal.
Name the first ion. Since the first ion is a
transition element, you must use a Roman
Numeral to represent the charge.
How do you know the charge?
Deductive reasoning.
Isn’t this easy
and FUN!
All compounds are neutral.
Oxygen has a -2 charge (group 16)
Therefore ….. Iron must have a +2 charge
since there is one iron and one oxygen. Iron
gets a Roman Numeral II.
Cu2S
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 16)
There are two coppers.
Copper I
Sulfide
Therefore each copper must have a +1 charge
for all ions to be neutral
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?
Manganese IV
oxide
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.
So why must we use Roman Numerals with transition
elements?
The metals in groups 1, 2, and 13 have single, definite
charges.
Group 1 metals have a +1 charge.
Group 2 metals have a +2 charge.
Group 13 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 andCuO
CuO We can’t just say Copper oxide. Which
CopperIII oxide
oxide one of these is Copper oxide? We must
Copper
distinguish these by using a Roman
Copperisis+2+1
Copper
Numeral
There are three transition elements which do not require a
Roman Numeral because they have single definite charges.
These are
Zinc – Zn+2
Cadmium –
Silver – Ag+1
Cd+2
You need to remember
the charges for these.
Ag2O
Name the first ion.
Silver oxide
Name the second ion
changing the suffix to –ide.
ZnCl2
Name the first ion.
Zinc chloride Name the second ion
changing the suffix to –ide.
No
Roman
Numerals
needed
for these.
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 element’s
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.
Cuprous = Copper I
Cupric = Copper II
Plumbous = Lead II
Plumbic = Lead IV
Ferrous = Iron II
Ferric = Iron III
There are many more – just be
familiar with these six common
names.
In Summary
Stock name
Common Name
Copper I
Cuprous
Copper II
Cupric
Iron II
Ferrous
Iron III
Ferric
Lead (II)
Plumbous
Lead (IV)
plumbic
How do you write formulas for binary ionic
compounds given the name?
Two simple steps:
1. Write the symbol and charge of each ion
2.Balance the charges by providing subscripts
Magnesium chloride
Write the symbol and charge of
each ion.
Mg+2
Cl-1
Cl-1 Balance the charges by supplying
subscripts. Subscripts tell how many of
each atom is present.
You need a second Cl-1 to balance the
2
charges
MgCl
More examples: Iron III bromide
Fe+3
Br -1
Br -1
Br -1
FeBr3
Write the symbol and charge of
each ion. The charge of the iron is
provided by the Roman Numeral.
Balance the charges by supplying
subscripts. The subscripts tell how
many of each ion is needed to
balance the compound.
You’ll need three bromine ions to
balance the one iron.
Aluminum Sulfide
Al+3
Al+3
S-2
S-2
S-2
Al2S3
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
How many aluminums are needed to
2
arrive at a +6 charge?
How many sulfurs are needed to arrive
at a -6 charge?
3
Second Category of compounds – Ternary Ionic
Compounds. These compounds contain at least one
polyatomic ion.
What is a polyatomic ion?
Let’s look at the name to try to understands.
It is an ion – that means it has a charge.
It is polyatomic – that means it is made of more
than one atom.
Simple as that!!
Let’s look at some examples of polyatomic ions.
CO3-2
carbonate
This ion is composed of one carbon
and three oxygens and the entire
group has a charge of -2.
Polyatomic ion – Group of atoms that act as a unit and
carry a charge.
-3
PO
Phosphate
4
More examples:
-2
SO4
SO3
-2
-1
ClO4
ClO3
-1
C2H3O2-1
Acetate
Sulfite
OH-1
Hydroxide
Perchlorate
NO3-1
Nitrate
NO2-1
Nitrite
Sulfate
Chlorate
ClO2-1 Chlorite
ClO-1 Hypochlorite
Ammonium
(only positive PI)
You need to learn these!!!
NH4+1
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 (NH4+1)
Three possible types of Ternary Ionic Compounds:
•Ammonium + negative ion (nonmetal)
s
Polyatomic
Ion
•Metal (positive ion) + negative polyatomic ion
•Ammonium + negative polyatomic ion
How do you name Ternary Ionic Compounds?
EASY! PIECE OF CAKE! NO PROBLEM!
Name the first ion.
Name the second ion. Isn’t that simple??!!
Examples:
When you look at this compound you
should recognize that this is NOT binary.
Na2CO3
There are THREE elements present.
Sodium carbonate When you see this, immediately look for
a polyatomic ion. Carbonate is present
Notice that you do here.
NOT change the
Name the first ion.
suffix – just name
the polyatomic ion Name the second ion.
A few more examples:
Fe(OH)3
Name the first ion.
Iron III hydroxide
Remember that iron requires a Roman
Numeral since it is a transition element.
What Roman Numeral should be used?
Since there are
3 OH groups,
each with a -1
The Roman Numeral comes from the
charge, the
charge of the ion. How do you find the
charge of the iron?
charge of the
iron must be +3 You know two things:
for the
•All compounds are neutral.
compound to be
•You know the charge of OH (-1)
neutral
Name the polyatomic ion.
NH4Cl
Name the first ion.
Ammonium chloride
Name the second ion.
Notice that since the second ion is a nonmetal that, like
binary ionic compounds, the suffix of the nonmetal changes
to –ide.
(NH4)3PO4
Name the first ion.
Ammonium phosphate
Name the second ion.
Looks like a monster, but it’s really simple...
ONE more example:
Name the first ion.
Cu2SO4
You should realize that you
need a Roman Numeral since
copper is a transition metal.
Copper I sulfate
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.
How do you write formulas for Ternary Ionic
Compounds?
Very much like writing formulas for Binary Ionic
Compounds.
Two steps:
•Write the formulas/symbols of each ion.
•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.
Let’s do some!!
Aluminum nitrate
Al+3
NO3-1
Al(NO3)3
First, you can tell from the name that
there is a polyatomic ion present
(nitrate). All binary ionic compounds
have suffixes of –ide.
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 Al+3
Since you will need a subscript of 3 for NO3-1, you need
to put this in parentheses with the 3 outside.
Lead (IV) acetate
Pb+4
C2H3O2-1
Pb(C2H3O2)4
Calcium phosphate
Ca+2
PO4-3
Ca3(PO4)2
Write the formula/symbol and charge
of each ion.
Balance the charges by supplying
subscripts. Since Pb is +4 and C2H3O2 is 1, you will need 4 C2H3O2-1 to balance
1Pb+4
Write the formula/symbol and charge
of each ion.
Balance the charges by supplying
subscripts. Since Ca is +2 and PO4 is -3,
you will need 3 Ca+2 to balance 2 PO4-3
The Third Category of Compounds – Binary
Molecular
What are Binary Molecular Compounds?
These compounds contain two elements (binary).
The term “molecular” indicates that these elements
are joined by a covalent bond.
They must therefore be nonmetals.
Bottom line – 2 elements – both nonmetals
To name and write formulas for these, you must
know some numerical prefixes.
Naming – you must use prefixes.
1 = mono
3 = tri
5 = penta
2 = di
4 = tetra 6 = hexa
7 = hepta
8 = octa
9 = nona
10 = deca
Steps
1. The first nonmetal only gets a numeric prefix
when there is more than one. No prefix if
there is only one.
2.The second element always gets a numeric
prefix and always has a suffix of -ide
CO2
Carbon dioxide
CO
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.
Carbon monoxide
N2O4
Dinitrogen tetraoxide
H2O
Dihydrogen monoxide
CCl4
Carbon tetrachloride
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.
Do you think it wise
to BAN DHMO?
AlCl3
What do you think about this one???
Be careful. This is a metal and nonmetal.
Always keep your Periodic Table in front of you
for reference.
You may have been tempted to say “aluminum
trichloride”. This is INCORRECT!
This is a binary IONIC compound. No prefixes are
used. Simply aluminum chloride.
Given the names of binary molecular compounds, how do
you write the formulas?
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!
Silicon dioxide Silicon and oxygen are both nonmetals.
SiO2
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.
Diphosphorous pentachloride
P2Cl5
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.
Nitrogen monoxide Nitrogen and oxygen are both
nonmetals.
NO
The lack of a prefix on nitrogen
means only ONE nitrogen.
The prefix “mono” on oxygen
indicates ONE oxygen.
Is this not sooooooo easy!??
What are Binary Acids?
Binary means two elements
Acid means it contains hydrogen
The second element is a nonmetal
hydrogen – nonmetal
Naming
All binary acids follow the pattern as shown below:
Prefix
Stem or root
of nonmetal
Hydro- < NM >
Suffix
-ic
Acid
HCl is a binary acid – hydrogen - nonmetal
HCl
Hydro chlor ic Acid
HI
Hydro iodic Acid
H2S
Hydrosulfur ic Acid
Given the name, how do you write formulas for binary acids?
The obvious pattern of the name tells you that it is a binary
acid. Hydro<NM>ic 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.
Hydrofluoric Acid
H+1
F-1
HF
The name tells you that this is a binary
acid.
Hydrophosphoric acid
H+1
P-3
H 3P
The name tells you that it is
definitely a binary acid.
Remember that the P has a -3 charge because it is in group
15
Let’s Practice
Ca(OH)2
Ternary Ionic
Calcium hydroxide
SO2
Binary molecular
Sulfur dioxide
(NH4)3PO4
Ternary Ionic
Ammonium phosphate
Co2(CO3)3
Ternary Ionic
Cobalt (III) carbonate
HBr
Hydrobromic acid
Binary acid
Potassium acetate
Ternary Ionic
KC2H3O2
Cadmium nitrate
Ternary Ionic
Cd(NO3)2
Aluminum oxide
Binary Ionic
Al2O3
Hydrosulfuric acid
Binary acid
H2S
Difluorine trioxide
F2O3
Binary molecular
The fifth category of compounds is Ternary
Acids.
These compounds begin with hydrogen since
they are “acids”.
Attached to the hydrogen is a polyatomic ion
Hydrogen – polyatomic ion
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
<Root of polyatomic ion>
HClO3
Chlor ic Acid
HNO3
Nitric Acid
H2SO4
Sulfur ic Acid
HCN
Cyan ic Acid
-ic acid
Ternary Acid – contains the
the polyatomic
polyatomic
ion cyanide
sulfate
ion nitrate
chlorate
(suffix
–ate).
–ide
(suffix
). –ate)
Second Category: If the polyatomic ion has a suffix
of –ite, use the following pattern:
suffix
<Root of polyatomic ion>
-ous acid
HNO2 Nitrous acid
Ternary acid contains polyatomic
ion, nitrite (-ite suffix).
HClO2 Chlor ous acid
Ternary acid contains polyatomic
ion, chlorite (-ite suffix).
H2SO3 Sulfur ous acid
Ternary acid contains polyatomic
ion, sulfite (-ite suffix).
How are Ternary Acids named?
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.
H+1 C2H3O2-1
This is a ternary acid.
HC2H3O2
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.
Hypochlorous acid
H+1
ClO-1
HClO
Phosphoric acid
H3PO4
This is a Ternary acid (does not begin
with “hydro-”.
The “-ous” suffix indicates that the
polyatomic ion in this acid has a suffix
of “-ite” - hypochlorite
Pretend that hydrogen is +1 and
balance the charges.
This is a Ternary acid (does not begin
with “hydro-”.
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.