UNIT 5: CHEMICAL FORMULAS AND CHEMICAL
NOMENCLATURE
Chemistry 1-2
Mr. Chumbley
CHEMICAL FORMULAS
AND IONS
EQ: How are elements and their ions represented within
chemical formulas?
Chemical Formulas
• A chemical formula is used to tell both number and kind of
atoms within a compound
• A chemical formula combination of chemical symbols
and numbers to represent a substance
• Examples of a chemical formula include:
• H 2O
• CO2
• C6H12O6
Chemical Formulas
• Within any chemical
formula, there are two
parts
C8H18
• Chemical symbols tell
you the kind of atoms
• Subscripts tell you the
number of each atom
or compound
Al2(SO
( 4) 3
Ions
• In order to name ionic compounds, we need to
understand what an ion is
• An ion is an atom or molecule that has gained or lost one
or more electrons and has a negative or positive charge
• Monatomic ions are made from a single atom
• Polyatomic ions are made of two or more atoms
Ions
• Similar to how atoms of the same element can have
multiple isotopes, atoms of the same element can have
multiple ions
• Cations are positively charged ions
• Anions are negatively charged ion
Naming Monatomic Ions
• Before we start looking at how to name compounds, it is
beneficial to know how to name single atoms
• All ions can be written using the chemical symbol and the
charge of the ion
• K+
• Mg2+
• F• N3-
• There are three ways to name monatomic ions based on
their location and charge
Naming Cations
• Cations are the simplest ion to name
• Cations use the name of the element, followed by the
numerical value of the charge, followed by the
positive/negative sign
Mg2+
• Is read as “magnesium two plus”
Naming Anions
• Anions are slightly more complicated
• Anions take the root of the element, and add “ide” to the
end
N3• Is read as “nitride”
Transition Metal Ions
• Element located in the middle of the table are called
transition metals, and can carry different charges
• Naming these ions uses a what is called the stock system
• This will be covered when we get to compounds that use
these particular ions
Ions on the
Periodic Table
Specific groups within the
periodic table can be
identified by the ions
elements within that
family form
H
2+
3+
4+
or
4– 3-
Li
Be
B
N
O
F
Na Mg
Al
P
S
Cl
1+
K
Alkali metals : 1+ (plus
Ag)
Alkaline Earth metals:
2+ (plus Zn and Cd)
Group 13 : 3+
Group 15 : 3 –
Group 16 : 2 –
Halogens : 1–
Ca
Zn Ga
Rb Sr
Ag Cd In
Cs Ba
Fr Ra
2- 1-
As Se Br
Te
I
Reflection!
• On the left side…
• Write the symbol and name of the ions that the first 20
elements form.
NAMING BINARY
COMPOUNDS
Binary Compounds
• All binary compounds contain only two elements
• Every binary compound ends with “ide”
• There are three types
Type I Binary Compounds
• Type I compounds are made up of a cation of fixed
charge, taken from either Group 1 or Group 2 on the
periodic table
• The anion from a Type I compound is taken from the
opposite side of the periodic table, taken from one of the
elements with fixed anions
• The net charge for the compound is always zero
Rules for Naming Type I Binary
Compounds
1. The cation is always named first and the anion second
2. A simple cation (obtained from a single atom) takes its
name from the name of the element
3. A simple anion (obtained from a single atom) is named
by taking the first part of the element name (the root)
and adding the letters “ide”
4. Write the name for the compound by combining the
names of the ions
Example 1-1
Name the compound RbI
• Rb is the chemical symbol for rubidium
• I is the chemical symbol for iodine
• Root is “iod”
• Add “ide” to the end to create iodide
• Put the two together to get the name rubidium iodide
Example 1-2
Name the compound CaO
• Ca is the chemical symbol for calcium
• O is the chemical symbol for oxygen
• Root is “ox”
• Add “ide” to the end to create oxide
• Put the two together to get the name calcium oxide
Example 1-3
Name the compound Li3N
• Li is the chemical symbol for lithium
• N is the chemical symbol for nitrogen
• Root is “nitr”
• Add “ide” to the end to create nitride
• Put the two together to get the name lithium nitride
Example 1-4
Write the formula for potassium sulfide.
• The chemical symbol of potassium is K
• Its ionic charge is +1
• Sulfide is derived from sulfur, whose symbol is S
• Its ionic charge is -2.
• The total positive charge must balance the total negative
charge
• Therefore, we need 2 potassium atoms to give a total positive
charge of +2 to balance the -2 charge of the sulfur.
• Putting it all together we have K2S
Example 1-5
Write the formula for magnesium chloride.
• The chemical symbol of magnesium is Mg
• Its ionic charge is +2
• Chloride is derived from chlorine, whose symbol is Cl
• Its ionic charge is -1.
• The total positive charge must balance the total negative
charge
• Therefore, we need 2 chlorine atoms to give a total negative
charge of -2 to balance the +2 charge of the magnesium
• Putting it all together we have MgCl2.
Type II Binary Compounds
• Type II compounds are formed from metals that are not
found in Group 1 or Group 2 of the periodic table
• The ionic charge of the metal in the compound is not
fixed, but the ionic charge of the nonmetal is
• The ionic charge of the metal is indicated through the use
of a Roman numeral
• This naming scheme is referred to as the stock system
Type II Cations
Transition metals are
capable of having multiple
ions of different charge
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Y
Zr
Nb Mo
Tc
Ru
Rh
Pd
Hf
Ta
Re
Os
Ir
Pt
W
Cu
Au
Ge
Hg
Tl
Sn
Sb
Pb
Bi
Po
At
Type II Binary Compounds
• Typically the charge of
Number
Roman Numeral
the metal is between
2-4
1
I
2
II
3
III
4
IV
5
V
6
VI
7
VII
8
VIII
9
IX
10
X
• Roman numerals are
used to indicate the
charge of the metal ion
Rules for Naming Type II Binary
Compounds
1. The cation is always named first and the anion second
2. A simple cation (obtained from a single atom) takes its
name from the name of the element
3. A Roman numeral indicates the ionic charge on the
metal cation.
4. A simple anion (obtained from a single atom) is named
by taking the first part of the element name (the root)
and adding the letters “ide”
5. Write the name for the compound by combining the
name of the cation, the Roman numeral, and the name
of the anion
Example 2-1
Name the compound FeCl2
• Fe is the chemical symbol for iron
• Fe is not in Group 1 or Group 2, therefore a Roman numeral is needed in the
name
• Cl is the chemical symbol for chlorine
• Root is “chlor”
• Add “ide” to the end to create chloride
• At this point we have iron (??) chloride
• To find the Roman numeral …
• Find the charge of the anion.
• Cl has a -1 charge.
• Multiply times the number of those atoms to get the total negative charge
• There are 2 Cl atoms, so the total negative charge is -2
• Balance total negative charge with total positive charge
• The total negative charge of -2 must be balanced with a total positive charge of +2
• Divide the total positive charge by the number of atoms to get Roman numeral
• Since there is only 1 Fe atom, the charge must be +2; so the Roman numeral is II
• Put the pieces together to get the name iron (II) chloride
Example 2-2
Name the compound PbS2
• Pb is the chemical symbol for lead
• Pb is not in Group 1 or Group 2, therefore a Roman numeral is needed in the
name
• S is the chemical symbol for sulfur
• Root is “sulf”
• Add “ide” to the end to create sulfide
• At this point we have lead (??) sulfide
• To find the Roman numeral …
• Find the charge of the anion.
• S has a -2 charge.
• Multiply times the number of those atoms to get the total negative charge
• There are 2 S atoms, so the total negative charge is -4
• Balance total negative charge with total positive charge
• The total negative charge of -4 must be balanced with a total positive charge of +4
• Divide the total positive charge by the number of atoms to get Roman numeral
• Since there is only 1 Pb atom, the charge must be +4; so the Roman numeral is IV
• Put the pieces together to get the name lead (IV) sulfide
Example 2-3
Write the formula for nickel (III) oxide
• The chemical symbol for nickel is Ni
• The ionic charge is +3, given by the Roman numeral
• Oxide is derived from oxygen, whose symbol is O
• Its ionic charge is -2
• At this point we have Ni O
• The total positive charge must balance the total negative
charge
• To balance the positive and negative charge, we find that the least
common multiple of 3 and 2 is 6
• This means that there are 2 Ni atoms to make +6 and 3 O atoms to
make -6
• Putting it all together we have Ni2O3
Example 2-4
Write the formula for lead (IV) nitride
• The chemical symbol for lead is Pb
• The ionic charge is +4, given by the Roman numeral
• Nitride is derived from nitrogen, whose symbol is N
• Its ionic charge is -3
• At this point we have Pb N
• The total positive charge must balance the total negative
charge
• To balance the positive and negative charge, we find that the least
common multiple of 3 and 4 is 12
• This means that there are 3 Pb atoms to make +12 and 4 N atoms
to make -12
• Putting it all together we have Pb3N4
Example 2-5
Write the formula for iron (II) oxide
• The chemical symbol for iron is Fe
• The ionic charge is +2, given by the Roman numeral
• Oxide is derived from oxygen, whose symbol is O
• Its ionic charge is -2
• At this point we have Fe O
• The total positive charge must balance the total negative
charge
• Since the charges are already balanced we know that there is 1 Fe
atom and 1 O atom
• Putting it all together we have FeO
Type III Binary Compounds
• Type III compounds
are compounds that
contain no metal ions
• The naming system for
this type of compound
is based on the
number of atoms of
each element
Number
Prefix
1
mono
2
di
3
tri
4
tetra
5
penta
6
hexa
7
hepta
8
octa
9
nona
10
deca
Rules for Naming Type III Binary
Compounds
1. The first element in the formula is named first, and the
full element name is used
2. The second element is named as though it were an
anion: root + “ide”
3. Prefixes are used to denote the numbers of atoms of
each element present
4. The prefix mono- is never used for naming the first
element.
Example 3-1
Name the compound NO2.
• N is the chemical symbol of nitrogen
• Since there is only one nitrogen atom AND it is the first element the
prefix mono is not used.
• O is the chemical symbol of oxygen, whose root is ox.
Add the -ide ending to get oxide
• There are two oxygen atoms so we also add the prefix di to get
dioxide
• Put the pieces together to get the name nitrogen dioxide
Example 3-2
Name the compound N2O.
• N is the chemical symbol of nitrogen
• Since there are two nitrogen atoms we need to add the prefix di to
get dinitrogen
• O is the chemical symbol of oxygen, whose root is ox.
Add the -ide ending to get oxide
• There is only one oxygen atom we add the prefix mono (mono IS
used for the second element) to get monoxide
• Put the pieces together to get the name dinitrogen
monoxide
Example 3-3
Write the formula for carbon tetrachloride.
• Carbon
• The chemical symbol of carbon is C
• No prefix before carbon means there is only 1 atom present
• Tetrachloride
• Chloride is derived from chlorine, whose symbol is Cl
• The prefix tetra means there are 4 atoms present
• Thus, there are 4 Cl atoms in the chemical formula
• Putting it all together we have CCl4
Example 3-4
Write the formula for dinotrogen pentaoxide.
• Dinitrogen
• The chemical symbol of carbon is N
• The prefix di before means there are 2 atoms present
• Thus, there are 2 N atoms in the chemical formula
• Pentaoxide
• Oxide is derived from oxygen, whose symbol is O
• The prefix penta means there are 5 atoms present
• Thus, there are 5 O atoms in the chemical formula
• Putting it all together we have N2O5
Binary Compound Review Whiteboarding
• We will be whiteboarding the answers to the homework
from last night
Number
Questions
Number
Questions
A
1, 11, 21
6
6, 16, 26
2
2, 12, 22
7
7, 17, 27
3
3, 13, 23
8
8, 18, 28
4
4, 14, 24
9
9, 19, 29
5
5, 15, 25
10
10, 20, 30
NAMING NON-BINARY
COMPOUNDS
EQ: How are compounds containing polyatomic ions
named?
Ternary Compounds
• Ternary compounds are those that contain polyatomic
ions
• Polyatomic ions are made up of more than one atom that
act as a single unit
• Most polyatomic ions have a negative charge, with the
notable exception of ammonium (NH41+)
• Nearly all polyatomic ions end with “ate” or “ite”
• Cyanide (CN1-)
• Hydroxide (OH1-)
• Peroxide (O22-)
Naming Ternary Compounds
• Naming ternary compounds is very similar to naming Type I or
Type II binary compounds
• If the polyatomic is first, the compound is named like a Type I
compound
• “name of polyatomic ion” + “root+ide”
• If the polyatomic ion is second and the cation is from Group 1
or Group 2, the compound is named like a Type I compound
• “name of element” + name of the polyatomic ion
• If the polyatomic ion is second and the cation is a transition
metal, the compound is named like a Type II compound
• “name of element” + (Roman numeral) + name of the polyatomic ion
Example 4-1
Name the compound NH4Cl.
• NH4+ is the chemical formula of ammoinum
• Since the polyatomic ion is first, no roman numeral is needed
• Cl is the chemical symbol of chlorine, whose root is chlor• Add the -ide ending to get chloride
• Put the pieces together to get the name ammonium
chloride
Example 4-2
Write the formula for ammonium sulfide.
• Ammonium is NH4+
• The charge of ammonium is known to be +1
• Sulfide is derived from sulfur, whose symbol is S
• The charge of sulfur is known to be -2
• The total positive charge must balance the total negative
charge
• There needs to be 2 ammonium ions to balance out the
charge of 1 sulfide ion
• Put the pieces together to get the name (NH4)2S
Example 4-3
Name the compound Na2SO4
• Na is the chemical symbol for sodium
• Since sodium is in Group 1, no Roman numeral is needed
• SO42- is the chemical symbol for a sulfate ion
• Put the two together to get the name sodium sulfate
Example 4-4
Name the compound CrPO4
• Cr is the chemical symbol for chromium
• Cr is not in Group 1 or Group 2, therefore a Roman numeral is needed in the
name
• PO4 is the chemical formula for a phosphate ion
• To find the Roman numeral …
• Find the charge of the anion.
• PO4 has a -3 charge.
• Multiply times the number of those atoms to get the total negative charge
• There is 1 PO4 ion, so the total negative charge is -3
• Balance total negative charge with total positive charge
• The total negative charge of -3 must be balanced with a total positive charge of +3
• Divide the total positive charge by the number of atoms to get Roman numeral
• Since there is only 1 Cr atom, the charge must be +3; so the Roman numeral is III
• Put the pieces together to get the name chromium (III) phosphate
Example 4-5
Write the formula for potassium cyanide
• The chemical symbol of potassium is K
• Its ionic charge is +1
• Since potassium is in Group 1, no Roman numeral is needed
• The formula for cyanide is CN• Its ionic charge is -1.
• The total positive charge must balance the total negative
charge
• Therefore, we need 1 potassium atoms balance the -1 charge
of the 1 cyanide ion
• Putting it all together we have KCN
Example 4-6
Write the formula for iron (III) chromate
• The chemical symbol of iron is Fe
• The Roman numeral tells us that the charge is +3
• The formula for chromate is CrO42• Its ionic charge is -2.
• The total positive charge must balance the total negative
charge
• To balance the positive and negative charge, we find that the least
common multiple of 2 and 3 is 6
• This means that there are 2 Fe atoms to make +6 and 3 CrO42- ions
to make -6
• Putting it all together we have Fe2(CrO4)3
Naming Polyatomic Ions with Oxygen
• There are a number of
polyatomic ions that are
very similar in name and
composition, with the
key difference being the
number of oxygen atoms
• The way in which these
ions are named is based
off the most common ion
Formula
CO32ClO3NO3PO43SO42-
Name
carbonate
chlorate
nitrate
phosphate
sulfate
Naming Polyatomic Ions with Oxygen
Number of Oxygen
Nomenclature
Two less oxygen
hypo___ite
One less oxygen
___ite
Most common
___ate
One more oxygen
per___ate
• The ion that is the
most common ends in
“ate”
• Ions with more or less
oxygen have names
based on the number
difference
Naming Polyatomic Ions with Oxygen
• Some examples:
Formula
Name
Formula
Name
PO53-
perphosphate
NO4-
pernitrate
PO43-
phosphate
NO3-
nitrate
PO33-
phosphite
NO2-
nitrite
PO23-
hypophosphite
NO-
hyponitrite
• While not all of these ions exist in the real world, the can
still be used to demonstrate the naming convention
Naming Acids
• For this class, all acids will begin with hydrogen (H)
• All acids end with the word “acid”
• There are two types of acids we will name:
• Acids that DO NOT contain oxygen
• Acids that DO contain oxygen
Naming Acids that Do Not contain Oxygen
• To name acids without oxygen, the nomenclature is
simple
1. The hydrogen is replaced with the prefix “hydro”
2. The suffix “ic” is added to the root of the non-hydrogen
anion
3. The word “acid” is added to the end
4. The result is in the form of hydro_____ic acid
Example 5-1
Name the compound HF.
• We know this is an acid because the chemical formula
starts with “H”
• Take the name of the anion (fluoride) add the prefix
“hydro” and change the ending to “ic”: hydrofluoric
• Finally, add the word “acid” to make hydrofluoric acid
Example 5-2
Name the compound HCN.
• We know this is an acid because the chemical formula
starts with “H”
• There is no oxygen present so we start with the prefix
“hydro”
• Next, take the name of the anion (cyanide) and change
the ending to “ic”: hydrocyanic
• Finally, add the word “acid” to make hydrocyanic acid
Example 5-3
Write the formula for hydrobromic acid.
• We know the formula starts with “H” because it is an acid
• The charge on H is +1
• We also know that the acid does not contain oxygen because of the
“hydro” prefix
• Removing the “hydro” and “ic” leaves us with “brom”, the root of
bromine or Br
• The charge on bromine is -1
• The total positive charge must balance the total negative charge
• There must be 1 H atoms to balance the charge of 1 bromine atom
• Balance the charges to get the formula HBr
Example 5-4
Write the formula for hydrosulfuric acid.
• We know the formula starts with “H” because it is an acid
• The charge on H is +1
• We also know that the acid does not contain oxygen because
of the “hydro” prefix
• Removing the “hydro” and “ic” leaves us with sulfur
• The charge on sulfur is -2
• The total positive charge must balance the total negative
charge
• There must be 2 H atoms to balance the charge of 1 sulfur atom
• Balance the charges to get the formula H2S
Naming Acids that Do Contain Oxygen
• Acids that contain oxygen will be polyatomic ions
1. Find the name of the polyatomic ion
2. If the name of the ion ends in “ate” change it to “ic”
3. If the name of the ion ends in “ite” change it to “ous”
4. Add the word acid to the end
5. The result is _____ic acid or _____ous acid
Example 6-1
Name the compound HClO4.
• We know this is an acid because it starts with “H”
• ClO4- is the perchlorate ion
• Change the “ate” to “ic” and get perchloric
• Add the word acid and get perchloric acid
Example 6-2
Name the compound H2SO3.
• We know this is an acid because it starts with “H”
• SO32- is the sulfite ion
• Change the “ite” to “ous” and get sulfous
• Add the word acid and get sulfous acid
• The name is actually sulfurous acid, which differs from the root for
sulfur.
Example 6-3
Write the formula for phosphorous acid.
• The word acid tells us the first element is “H”
• The charge on H is +1
• We also know it is a ternary acid because the prefix “hydro”
(meaning binary acid) is missing
• Change “ous” to “ite” to get phosphite
• The formula for phosphite is PO33• The total positive charge must balance the total negative
charge
• There must be 3 H atoms to balance the charge of 1 phosphite ion
• Putting it together and balancing the charges we get H3PO3
Example 6-4
Write the formula for carbonic acid.
• The word acid tells us the first element is “H”
• The charge on H is +1
• We also know it is a ternary acid because the prefix “hydro”
(meaning binary acid) is missing
• Change “ic” to “ate” to get carbonate
• The formula for carbonate is CO32• The total positive charge must balance the total negative
charge
• There must be 2 H atoms to balance the charge of 1 carbonate ion
• Putting it together and balancing the charges we get H2CO3
Hydrates
• Many of the Type I, Type II, and Ternary compounds are
categorized as inorganic salts
• When some of these salts form, they crystalize with water
molecules
• The amount of water molecules in the compound is a
whole number ratio and is written as part of the formula
MgSO4 ∙ 7H2O
Naming Hydrates
• The salt portion of the
hydrate is named as it
exists without the
water
• The number of water
molecules is indicated
by using the numerical
prefixes before the
word “hydrate”
Number
Prefix
1
mono
2
di
3
tri
4
tetra
5
penta
6
hexa
7
hepta
8
octa
9
nona
10
deca
Example 7-1
Name the compound AlCl3·6H2O
• The name of the salt is as it would be named without the
water, aluminum chloride
• The hydrate portion contains 6 molecules of water, so it
becomes hexahydrate
• Put both parts together to get aluminum chloride
hexahydrate
Example 7-2
What is the chemical formula for sodium sulfate
decahydrate?
• The chemical formula for sodium sulfate is Na2SO4
• The hydrate has the prefix of deca, meaning there are 10
H2O molecules
• The formula is written as Na2SO4·10H2O