Transcript Naming Compounds and Writing Formulas

Naming Compounds and
Writing Formulas
Module 12
Ban DHMO?
• DHMO is dihydrogen monoxide.
• Evaluate the following link and
decide if this potentially
dangerous chemical should be
prohibited.
• www.dhmo.org
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
NaCl
Sodium Chloride
What is the name of this
compound:
HIJKLMNO?
Name
the metal ion
WATER – “H” to “O”
CaO
Calcium Oxide
Al2S3
Aluminum Sulfide
You have to admit – that was
funny!
Name the nonmetal
ion, changing the
suffix to –ide.
MgI2
Magnesium Iodide
BaNa2
Thisshould
is two of
metals
not
a binary
ionic
The
name
this is–Banana
(JOKE
– this
haha)
You
recognize
a problem
with
one
compound
What about the transition metals and using
roman numerals? How does that work? Let’s see.
FeO
Iron II Oxide
Isn’t this
easy and
FUN!!!
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.
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)
Copper I
Sulfide
There are two coppers.
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.
Manganese IV
oxide
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.
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 and CuO We can’t just say Copper oxide.
Copper II
I oxide
oxide Which one of these is Copper oxide?
We must distinguish these by using a
Copper is +2
+1
Roman 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 –
Cd+2
Silver – Ag+1
Ag2O
Silver oxide
ZnCl2
Zinc chloride
You need to remember
the charges for these.
No
Name the second ion
Roman
changing the suffix to –ide.
Numerals
Name the first ion.
needed
Name the second ion
for these.
Name the first ion.
changing the suffix to –ide.
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
Ferrous = Iron II
Cupric = Copper II
Ferric = Iron III
There are many more – just be
familiar with these six common
names.
Plumbous = Lead II
Plumbic = Lead IV
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
Mg+2
Cl-1
Cl-1
MgCl2
Write the symbol and charge of
each ion.
Balance the charges by supplying
subscripts. Subscripts tell how
many of each atom is present.
You need a second Cl-1 to balance
the charges
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 arrive at a +6 charge? 2
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:
SO4
-2
SO3
-2
ClO4
-1
ClO3
-1
Sulfate
C2H3O2-1
Acetate
Sulfite
OH-1
Hydroxide
Perchlorate
NO3-1
Nitrate
NO2-1
Nitrite
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:
Polyatomic Ions
•Ammonium + negative ion (nonmetal)
•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
Na2CO3
binary. There are THREE elements
Sodium carbonate present. When you see this,
immediately look for a polyatomic ion.
Notice that you do Carbonate is present here.
NOT change the
suffix – just name Name the first ion.
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
Since there are transition element. What Roman
3 OH groups,
Numeral should be used?
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
•You know the charge of OH (-1)
be 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 a pussycat.
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
Write the formula/symbol and
charge of each ion.
Balance the charges by supplying
Pb(C2H3O2)4 subscripts. Since Pb is +4 and
C2H3O2 is -1, you will need 4
C2H3O2-1 to balance 1Pb+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 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
2 = di
5 = penta
4 = tetra 6 = hexa
7 = hepta
9 = nona
8 = octa
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
Name the first element. Since
there is only one, no prefix is
Carbon dioxide needed. The second element
always
gets
a
prefix
and
a
suffix
of
CO
–ide.
Carbon monoxide
Name the first element.
Since there are two present,
N2O4
the prefix “di” is needed. The
Dinitrogen tetraoxide second element always gets
a prefix and a suffix of –ide.
H2O
Dihydrogen monoxideDo you think it wise
to BAN DHMO?
CCl4
Carbon tetrachloride
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
SiO2
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.
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
NO
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.
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
Suffix
Hydro- < NM > -ic
Acid
HCl is a binary acid – hydrogen - nonmetal
HCl
Hydrochloric Acid
HI
Hydroiodic Acid
H2S
Hydrosulfuric 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
HF
F-1
The name tells you that this is a
binary acid.
Hydrophosphoric acid
H+1
P-3
The name tells you that it is
definitely a binary acid.
H3P
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
Nitr ic Acid
H2SO4
Sulfur ic Acid
HCN
Cyan ic Acid
-ic acid
Ternary Acid – contains
the polyatomic ion sulfate
nitrate
chlorate
(suffix
cyanide
–ate).
(suffix
(suffix –ide).
–ate)
Second Category: If the polyatomic ion has a
suffix of –ite, use the following pattern:
suffix
<Root of polyatomic ion>
HNO2 Nitrous acid
HClO2 Chlorous acid
-ous acid
Ternary acid contains
polyatomic ion, nitrite (-ite
suffix).
Ternary acid contains
polyatomic ion, chlorite (-ite
suffix).
H2SO3 Sulfurous 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.
The “-ic” suffix in the acid name tells you
HC2H3O2 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 This is a Ternary acid (does not
begin with “hydro-”.
+1
-1
H
ClO
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.
Phosphoric acid This is a Ternary acid (does not
begin with “hydro-”.
HClO
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.
This concludes Module 13!