Molecules,
Compounds &
Chemical Equations
Bonding
Two (or more) atoms will bond together
because the combined product is more stable
than the individual atoms.
The atoms combine or bond by sharing
electrons and forming covalent bonds, or
transferring electrons to for ionic bonds.
Covalent Bonds
When electrons are shared between atoms, a
molecule is formed. The arrangement of the
atoms and bonds in the molecule will have a
great effect on the properties of the molecule.
Homonuclear Diatomic Elements
Some elements exist in nature as molecules.
Common elements that exist bonded together
by covalent bonds are:
H2, N2, O2, F2, Cl2, Br2, and I2
Covalent Bonds - Chlorine
Covalent bonds
occur between nonmetals. Electrons are
shared, and the
shared electrons hold
the atoms together so
they function as a unit
called a molecule.
Elements & Compounds
Ionic Bonding
When metals combine with non-metals, a
transfer of electrons occurs, from the metal to
the non-metal.
The resulting attraction between oppositely
charged ions is called an ionic bond. Although
this attraction is very strong, the ions can be
separated when dissolved in substances such as
water.
Types of Bonds
In ionic bonding,
the coulombic attraction
between oppositely
charged ions in a
crystal, forms very
stable compounds.
Ionic Bonding
The strength of ionic bonds comes from the
crystal structure. Every cation is surrounded by
anions, and every anion is surrounded by
cations. The resulting coulombic attraction
between oppositely charged ions creates very
stable substances.
Ionic Bonding
Lattice Energy is a measure of the strength of
ionic bonding in a crystal. It is the energy
change that takes place when gaseous ions come
together to form a mole of an ionic solid.
M+(g) + X-(g) MX(s)
Ionic Bonding
Ionic bonds result
from the electrostatic
attraction of
oppositely charged
ions. There is no
electron sharing
between ions.
Ionic Bonding
Electrons are
transferred
from the metal
to the nonmetal, creating
ions. The
oppositely
charged ions
attract each
other, forming
ionic bonds.
Electron Configurations of Ions
The atoms of the main group elements
(groups IA-VIIA) will form ions by losing or
gaining electrons. The resulting ion will have
the same electron configuration as a noble gas
(group VIIIA). These configurations are usually
very stable.
Common Ionic Charges
The charges of ions of elements in groups
1A-7A (the main groups) are usually predictable.
Group 1A metals form +1 ions, group 2A
metals form +2 ions, etc.
The non-metals of group 5A have a -3
charge, those of group 6A have a -2 charge, and
the halogens form ions with a -1 charge.
Typical Ionic Charges
Naming Inorganic Compounds
1. Binary Compounds
Binary compounds contain only two elements.
The elements are either a metal with a nonmetal (ionic bonding), or two non-metals
(covalent bonding).
Naming Binary Compounds
a) Metal + Non-metal:
When metals react with non-metals, the metal
loses electrons and the non-metal gains
electrons. The resulting attraction between
oppositely charged ions creates ionic bonds.
Common Ionic Charges
The charges of ions of elements in groups
1A-7A (the main groups) are usually predictable.
Group 1A metals form +1 ions, group 2A
metals form +2 ions, etc.
The non-metals of group 5A have a -3
charge, those of group 6A have a -2 charge, and
the halogens form ions with a -1 charge.
Typical Ionic Charges
Naming Binary Compounds
For example, NaCl is called
sodium chloride
Where “chlor” is the root for the element
chlorine.
Naming Binary Compounds
Three common transition metals also have
only one ionic charge, and are also named the
same way.
They are: zinc ion (always +2), silver ion
(+1) and cadmium ion (+2)
ZnS is zinc sulfide, as “sulf” is the root for
sulfur.
Writing Formulas of Binary
Compounds
Compounds have no net charges, so the
formulas of ionic compounds must contain
equal numbers of positive and negative charges.
Magnesium bromide, made from magnesium
ion (Mg2+) and bromide ion (Br1-) has the
formula
MgBr2
Binary Compounds with Variable
Charge Metals
Most transition metals and the metals on the
lower right side of the periodic table can have
several ionic charges.
The properties of the ion vary greatly with
charge, so the charge must be specified in
naming the ion or its compounds.
Typical Ionic Charges
Binary Compounds with Variable
Charge Metals
Binary Compounds with Variable
Charge Metals
If an ion has variable charges, you must
specify the charge in naming the metal.
If an ion has only one charge, it is incorrect
to specify its charge.
Naming Fe2O3

Fe2O3 is an iron oxide, but we must specify the
charge of the iron ion.
We know each oxide has a -2 charge, so
three oxide ions have a total charge of -6.
The two iron ions therefore have a charge of
+6, with each iron having a charge of +3.
The name of the compound is iron(III) oxide.
Naming Covalent Binary
Compounds
b) When two non-metals form a compound, they
share electrons, rather than transfer them. The
resulting bond is called a covalent bond.
The naming of these compounds is fairly
simple. The first element is named first, and
the second element is named as the root + ide.
Prefixes are used to indicate the number of
each atom present.
Naming Covalent Binary
Compounds
These prefixes are
used only for
compounds containing
two non-metals.
The prefix mono is
never used for the first
element in the
compound.
Naming Covalent Binary
Compounds

The prefix mono is never used for the first
element. CO2 is carbon dioxide.

If the prefix ends in an a or o, and the element
that follows begins with a vowel, the last letter
of the prefix is usually dropped. N2O5 is called
dintrogen pentoxide (and not pentaoxide).
Naming Covalent Binary
Compounds

Note that these prefixes are only used for binary
covalent compounds. It is incorrect to use them
for compounds containing a metal and a nonmetal.
Naming Binary Compounds
c) Naming of Binary Acids
Binary acids are aqueous solutions of
compounds with the general formula HX,
where X represents a non-metal.
When hydrogen forms compounds with nonmetals, the bonds are always covalent, with
electrons shared between the two elements.
Naming Binary Acids
The naming of the pure compound and its
aqueous acid solution differ.
HCl is a gas called hydrogen chloride.
HCl(aq) is an acid called hydrochoric acid.
Naming Binary Acids

Name the following acids:
H2S(aq) , HBr(aq)
Unusual Ions
Mercury forms two ions, mercury(I) and
mercury(II). The mercury(I) ion is polyatomic,
and exists as two mercury(I) ions bonded
together. Its formula is Hg22+.
Oxygen in compounds usually exists as the
oxide ion, O2-. Oxygen also exists as the
peroxide ion, O22-, with each oxygen having a -1
charge.
Naming Polyatomic Ions
There are many ions, such as sulfate or
nitrate, that contain more than one element.
Many of these ions contain oxygen and a
non-metal.
These ions can be found in a group of acids
called the oxy acids.
Naming the Oxy Acids
The easiest way to learn the names of the
ions is to memorize a short list of oxy acid
names and their formulas.
The names of the ions are derived from the
names of the acids.
Keep in mind that the acids must be aqueous
solutions.
Common Oxy Acids
Acid
HNO3
Name
H2SO4
Sulfuric acid
HClO3
Chloric acid (or iodic or bromic acid)
H3PO4
Phosphoric acid
H2CO3
Carbonic acid
Nitric acid
Naming Complex Ions
Once the list of acids is learned, the names
of other acids and ions can be derived.
Removal of the hydrogens in the acid as H+
ions results in ions that end in ate.
HNO3 minus one H+ ion gives NO31-, the
nitrate ion.
The oxy acids that end in ic, produce ions
that end ate.
Naming Complex Ions
Sulfuric acid is H2SO4. Removing two H+
ions produces SO42-, the sulfate ion.
Keep in mind that the formula of the ions
must include the charge.
If only one of the H+ ions is removed from
sulfuric acid, HSO41- is produced. This is called
the hydrogen sulfate ion, also commonly known
as the bisulfate ion.
Naming Complex Ions
Carbonic acid, H2CO3, produces two ions:
HCO31-, the hydrogen carbonate or
bicarbonate ion
and
CO32-, the carbonate ion
Naming Complex Ions
Some of the oxy acids previously listed also
exist with one more oxygen in the formula.
HClO3, HBrO3 and HIO3 , in aqueous
solution are chloric, bromic and iodic acid
respectively.
Adding an oxygen to the formulas provides
the formulas for the per root ic acid.
HClO4 is perchloric acid. The ion, ClO41- is the
perchlorate ion.
Naming Complex Ions
Several of the oxy acids listed previously can
have one less oxygen atom in the formula.
These acids have names that end in ous, and ions
that end in ite.
HNO3 is nitric acid. HNO2(aq) is nitrous
acid. The ion NO21- is the nitrite ion.
Naming Complex Ions
Sulfuric acid, phosphoric acid, chloric,
bromic and iodic acids all can have one less
oxygen atom. The acids are sulfurous acid,
phosphorous acid, chlorous acid, bromous acid
and iodous acid.
The ions are called sulfite, phosphite,
chlorite, bromite and iodite ion.
Naming Complex Ions
The halogen oxy acids HClO3, HBrO3, and
HIO3 also exist with two less oxygen atoms in
the formula. The name of the resulting acid has
the name
hypo root ous acid.
HClO(aq) is hypochlorous acid, and ClO1- is
the hypochlorite ion.
Naming Complex Ions

If you memorize the list of acids ending in ic,
you can derive the names and formulas for many
other acids and ions.
Acid
HNO3
H2SO4
HClO3
H3PO4
H2CO3
Name
Nitric acid
Sulfuric acid
Chloric acid (or iodic or bromic acid)
Phosphoric acid
Carbonic acid
Naming Complex Ions



In naming the ions from the acids on the list,
remember that ic  ate.
If there is one additional oxygen atom, the acid
has the name per root ic, and the ion has the
name per root ate.
If there is one less oxygen atom, the acid has a
name ending in ous. The ions will have names
ending in ite. (ous ite)
Naming Complex Ions

If an acid has two less oxygen atoms than the
“ic” list, its name has the form hypo root ous.
The ion will have the name hypo root ite.
Other Common Formulas
CH3COOH
CH3COO1NH3
NH4+
OH1H3O+
MnO41CrO42Cr2O72-
Acetic acid
Acetate ion
Ammonia
Ammonium ion
Hydroxide ion
Hydronium ion
Permanganate ion
Chromate ion
Dichromate ion
Chemical Composition
Chemical composition can be expressed in
several ways, including percentages by mass, or
chemical formulas.
For example, water contains 11.2%
hydrogen and 88.8% oxygen by mass. This
information must be consistent with the
chemical formula for water, H2O.
Chemical Composition
For example, water contains 11.2% hydrogen
and 88.8% oxygen by mass. This information
must be consistent with the chemical formula
for water, H2O.
2 H atoms = 2(1.008 amu) = 2.016 amu
1 O atom =1( 16.00 amu) =16.00 amu
molecular mass of water = 18.02 amu
% H = (2.016/18.02) x 100% = 11.19%H
% O = (16.00/18.02) x 100% = 88.79%O
Chemical Composition
The early scientists analyzed new chemical
compounds to determine their composition and
chemical formulas. Modern analytical laboratories
still provide this service.
Chemical Composition
Usually, the compound is combusted in the
presence of oxygen. Any carbon in the compound
is collected as carbon dioxide (CO2), and any
hydrogen is collected as water (H2O).
Chemical Composition
Similar techniques exist to analyze for other
elements.
The formula obtained for the compound is
the simplest whole number ratio of the elements
in the compound, or the empirical formula. It may
differ from the actual formula. For example,
hydrogen peroxide is H2O2, but chemical
analysis will provide an empirical formula of
HO.
Determining Empirical Formulas
If given % composition:
1. Assume a quantity of 100 grams of the
compound.
2. Determine the number of moles of each
element in the compound by dividing the
grams of each element by the appropriate
atomic mass.
3. To simplify the formula into small whole
numbers, divide the moles of each element
by the smallest number of moles.
Determining Empirical Formulas
4. If necessary, multiply each number of moles
by a factor that produces whole number
subscripts.
5. If you know the approximate molar mass of
the compound, determine the molecular
formula.
% Composition Problem

An oxide of titanium contains 59.9% titanium.
Determine the empirical formula of the
compound.
Determining Empirical Formulas
If given combustion data:
The ultimate goal is to get the simplest whole
number ratio of the elements in the
compound. Usually the compound contains
carbon, hydrogen and perhaps oxygen or
nitrogen.
1. Use the information about CO2 to
determine the moles and mass of carbon in
the compound.
Determining Empirical Formulas
If given combustion data:
2. Use the information about H2O to
determine the moles and mass of hydrogen
in the compound.
3. The mass and moles of oxygen (or a third
element) can be obtained by difference.
4. Once moles of each element is obtained,
find the relative number of moles and
empirical formula (as with % composition).
Formulas from
Combustion
Data
This method assumes
the compound
contains only C and
H.
Empirical Formula using
Combustion Data- Problem

A compound, which contains C, H and O, is
analyzed by combustion. If 10.68 mg of the
compound produces 16.01 mg of carbon dioxide
and 4.37 mg of water, determine the empirical
formula of the compound.
If the compound has a molar mass of 176.1
g/mol, determine the molecular formula of the
compound.
Stoichiometry


Stoichiometry is a Greek word that means using
chemical reactions to calculate the amount of
reactants needed and the amount of products
formed.
Amounts are typically calculated in grams (or
kg), but there are other ways to specify the
quantities of matter involved in a reaction.
Stoichiometry
A balanced chemical equation or reaction is
needed before any calculations can be made.
The formulas of all reactants and products
are written before attempting to balance the
equation.
Balancing Chemical EquationsProblem

Sodium metal reacts with water to produce
aqueous sodium hydroxide and hydrogen.
Balancing Chemical EquationsProblem

Sodium metal reacts with water to produce
aqueous sodium hydroxide and hydrogen.
Na(s) + H2O(l ) 
Balancing Chemical EquationsProblem

Sodium metal reacts with water to produce
aqueous sodium hydroxide and hydrogen.
Na(s) + H2O(l )  NaOH(aq) + H2(g)
Balancing Chemical EquationsProblem

Sodium metal reacts with water to produce
aqueous sodium hydroxide and hydrogen.
Na(s) + H2O(l )  NaOH(aq) + H2(g)

The equation is not yet balanced. Hydrogens
come in twos on the left, and three hydrogens
are on the right side of the equation.
Balancing Chemical EquationsProblem

Sodium metal reacts with water to produce
aqueous sodium hydroxide and hydrogen.
Na(s) + H2O(l )  NaOH(aq) + H2(g)

Try a “2” in front of the water.
Balancing Chemical EquationsProblem

Sodium metal reacts with water to produce
aqueous sodium hydroxide and hydrogen.
Na(s) + 2 H2O(l )  NaOH(aq) + H2(g)

We now have two O atoms on the left, so we
need to put a 2 before NaOH.
Balancing Chemical EquationsProblem

Sodium metal reacts with water to produce
aqueous sodium hydroxide and hydrogen.
Na(s) + 2 H2O(l ) 2NaOH(aq) + H2(g)

The two sodium atoms on the right require that
we put a 2 in front of Na on the left.
Balancing Chemical EquationsProblem

Sodium metal reacts with water to produce
aqueous sodium hydroxide and hydrogen.
2 Na(s) + 2 H2O(l ) 2NaOH(aq) + H2(g)

The two sodium atoms on the right require that
we put a 2 in front of Na on the left. The
equation is now balanced.
Balancing Chemical EquationsProblem

Sodium metal reacts with water to produce
aqueous sodium hydroxide and hydrogen.
2 Na(s) + 2 H2O(l ) 2NaOH(aq) + H2(g)
Left Side
Right Side
Na- 2
Na- 2
H- 4
H- 4
O- 2
O- 2
Chemical Equations
2 Na(s) + 2 H2O(l ) 2NaOH(aq) + H2(g)
The balanced chemical equation can be
interpreted in a variety of ways.
It could say that 2 atoms of sodium react
with 2 molecules of water to produce 2
molecules of sodium hydroxide and a molecule
of hydrogen.
Chemical Equations
2 Na(s) + 2 H2O(l ) 2NaOH(aq) + H2(g)
The balanced chemical equation can be
interpreted in a variety of ways.
It could say that 200 atoms of sodium react
with 200 molecules of water to produce 200
molecules of sodium hydroxide and 100
molecules of hydrogen.
Chemical Equations
2 Na(s) + 2 H2O(l ) 2NaOH(aq) + H2(g)
The balanced chemical equation can be
interpreted in a variety of ways.
 It is usually interpreted as 2 moles of sodium
will react with 2 moles of water to produce 2
moles of sodium hydroxide and 1 mole of
hydrogen.
 The balanced equation tells us nothing about the
masses of reactants or products.