Transcript Naming Compounds and Writing Formulas

Key
Question:
Why Do Atoms Combine In Certain Ratios?
Review of Oxidation
Numbers
Review of Oxidation Numbers
 All
compounds have an electrical charge of zero
(they are neutral).
 An oxidation number indicates the charge on the
atom (or ion) when electrons are lost, gained, or
shared in chemical bonds.
Oxidation Numbers
 A sodium
atom always ionizes
to become Na+ (a charge of
+1) when it combines with
other atoms to make a
compound.
 Therefore, we say that sodium
has an oxidation number of 1+.
What is chlorine’s oxidation number?
H
He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
1 2 3 4 5 6 7 8
The Number Of Electrons In The
Outside Shell.
Ionic Bonds
 On
the periodic table, strong electron donors are on the
left side (alkali metals).
 Strong electron acceptors are on the right side
(halogens).
 The further apart two elements are on the periodic table,
the more likely they are to form …
 an ionic compound.
Covalent Bonds
 Covalent
compounds form when elements have roughly
an equal tendency to accept electrons.
 Elements that are both nonmetals and therefore close
together on the periodic table tend to form covalent
compounds.
Oxidation Numbers, Lewis Structures And
Chemical Formulas
 Remember,
the oxidation numbers for all the atoms in a
compound must add up to zero.
Chemical Compound Quiz
Sodium chloride is a flavorful addition to many
foods. What is the common name?
Salt
Multiple Oxidation Numbers
 Some
periodic tables list
multiple oxidation numbers
for most elements.
 This is because more
complex bonding is possible.
Euphemisms in Science
We all know that some politicians and government spokesmen
use certain euphemistic phrases to give an aura of respectability
to descriptions of events or actions which would be offensive
when expressed in plain English. The following is a list of
Euphemisms in Science and their translations into plain English.
“It has long been known...”
I haven't bothered to look up any references!
Naming Compounds and
Writing Formulas
3 Types Of Chemical Compounds
•Binary ionic
- metal ion – nonmetal ion
•Ternary ionic
- at least one ion is a
polyatomic ion
•Binary molecular
- two nonmetals
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
stairstep on the Periodic Table.
Naming Binary Compounds
 A binary
ionic compound is held together by ionic
bonds.
 Binary molecular compounds consist of covalently
bonded atoms.
 Each type of compound has its own naming rules.
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 or
tin or lead, 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
CaO
Calcium Oxide
Al2S3
Aluminum Sulfide
MgI2
Magnesium Iodide
Name the metal ion
Name the nonmetal ion,
changing the suffix to –ide.
Examples
BaNa2
This is two metals – not a binary ionic
You
Theshould
name recognize
of this is Banana
a problem
(haha!!)
with this one
compound
What is the name of this
compound:
HIJKLMNO?
WATER – “H” to “O”
You have to admit – that was
funny!
What About The Transition Metals And Using
Roman Numerals? How Does That Work?
Let’s See.
Notice – metal and nonmetal.
Name the first ion. Since the first ion is a
FeO
transition element, you must use a Roman
Iron(II)Oxide Numeral to represent the charge.
How do you know the charge?
Deductive reasoning.
•All compounds are neutral.
•Oxygen has a -2 charge (group 16)
Isn’t this easy
and FUN!!!
•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
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) It is the same as the charge.
oxide
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.
Things You Can Learn
From Your Dog!!
•
When it is hot outside, drink lots of water.
•
Take naps.
So Why Must We Use Roman Numerals With
Transition Elements?
•The metals in groups 1, 2, 3, and 13 have single, definite
charges.
•Group 1 metals have a +1 charge.
•Group 2 metals have a +2 charge.
•Groups 3 and 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
Copper II
I oxide
oxide
Copper is +2
+1
We can’t just say Copper oxide. Which one
of these is Copper oxide? We must
distinguish these by using a Roman Numeral
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
MgCl2
Write the symbol and charge of each ion.
Cl-1 Balance the charges by supplying
Cl-1 subscripts. Subscripts tell how many of
each atom is present.
You need a second Cl-1 to balance the
charges
Iron (III) bromide
Fe+3
FeBr3
Br -1 Write the symbol and charge of each
Br -1 ion. The charge of the iron is provided
Br -1 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
Al2S3
S-2
S-2
S-2
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
Writing Formulas a Little Quicker
Iron and oxygen combine to form a compound.
Iron (Fe) has an oxidation number of 3+.
Oxygen (O) has an oxidation number of 2–.
Predict the chemical formula of this compound.
Writing Formulas a Little Quicker
3+
2-
Fe 2 O 3
Let’s Try Another One:
Manganese (IV) phosphide
4+
3-
Mn 3 P 4
Let’s Try One More:
Manganese (IV) oxide
4+
2-
Mn 2 O 4
MnO2
Exit Quiz – Formula for magnesium chloride?
2+
MgCl2
1-
Murphy's Laws
of
Science and Technology
Logic is a systematic method of coming to the
wrong conclusion with confidence.
Exit Quiz – Formula for sodium oxide?
1+
2-
Na2O
Exit Quiz – Name for:
6+ 6-
3+ 2-
Fe2O3
Iron (III) oxide
Exit Quiz – Formula for:
4+ 2-
Cr O
2
Chromium (IV) oxide
4
CrO2
Familiar Saying
Socially orientated individuals tend to
congregate in gregariously homogenous
groupings.
Birds of a feather flock together!!
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.
You have a page of other polyatomic ions
You will need these for the rest
of the year!!!
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 Ion
•Ammonium
+ negative ion (nonmetal)
•Metal (positive ion)
+ negative polyatomic ion
•Ammonium
+ negative polyatomic ion
How Do You Name Ternary Ionic Compounds?
Name the first ion.
Name the second ion. Isn’t that simple??!!
Examples:
When you look at this compound you
Na2CO3
should recognize that this is NOT binary.
There are THREE elements present. When
Sodium carbonate you see this, immediately look for a
polyatomic ion. Carbonate is present here.
Notice that you do
NOT change the
suffix – just name the
Name the first ion.
polyatomic ion
Name the second ion.
Fe(OH)3
Name the first ion.
Iron (III) hydroxide Remember that iron requires a
Roman Numeral since it is a
Since there
transition element. What Roman
are 3 OH
Numeral should be used?
groups, each
The Roman Numeral comes from the
with a -1
charge of the ion. How do you find
charge, the
the charge of the iron?
charge of the
iron must be
+3 for the
compound to
be neutral
You know two things:
•All compounds are neutral.
•You know the charge of OH (-1)
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.
Cu2SO4
Copper (I) sulfate
Name the first ion.
You should realize that you need
a Roman Numeral since copper
is a transition metal.
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.
Three Steps:
1. Write the formulas/symbols of each ion.
2. Balance the charges by supplying subscripts.
3. 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
Al3+
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
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
Calcium phosphate of each ion.
Ca+2
Ca3(PO4)2
PO4-3
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
Exit Quiz
 Al3+
combines with sulfate (SO4)2– to make aluminum
sulfate.
 Write the chemical formula for aluminum sulfate.
Exit Quiz Answer
3+
2-
Al 2 (SO4) 3
Overall Strategy For Naming
Chemical Compounds.
Let’s Try Another One:
Manganese (IV) phosphate
4+
3-
Mn3 (PO4)
4
Let’s Try One More:
Manganese (IV) carbonate
4+
2-
Mn (CO3)
2
4
Mn(CO3)2
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
7 = hepta
9 = nona
2 = di
4 = tetra
6 = hexa
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
Carbon dioxide
CO
Carbon monoxide
N2O4
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.
Dinitrogen tetraoxide
H2 O
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.
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 name it
aluminum chloride.
Given The Names Of Binary Molecular Compounds,
How Do You Write The Formulas?
Very easily done!!! 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
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!??
Familiar Saying
It is fruitless to attempt to indoctrinate a
superannuated canine with innovative
maneuvers.
You can’t teach an old dog new tricks!
A Flow Chart For Naming Binary Compounds
Exit Quiz
CO2
SO3
Carbon dioxide
Sulfur trioxide
SO
CO
Sulfur monoxide
Carbon monoxide
N2O5
B2O3
Dinitrogen pentaoxide
Diboron trioxide
CF4
NF5
Carbon tetrafluoride
Nitrogen pentafluoride