Inorganic Compounds
Compounds & Chemical Formulas
• COMPOUNDS are a combination of 2 or more
elements in definite ratios by mass.
 The character of each element is lost when forming a
compound.
NaCl, salt
• CHEMICAL FORMULAS use atomic symbols
and subscripts to describe the smallest unit of a
compound that retains the characteristics of the
compound.
Ethanol, C2H6O
Buckyball, C60
CHEMICAL FORMULAS
• Formula for glycine is C2H5NO2
• In one molecule there are
2 C atoms
5 H atoms
1 N atom
2 O atoms
What is the molar
mass of ethanol,
C2H6O?
MOLECULAR WEIGHT AND
MOLAR MASS
• Molecular weight
1 mol contains
sum of the atomic weights of all atoms in the
molecule (amu).
2 mol C (12.01 g C/1 mol) = 24.02 g C
• Molar mass
6 mol H (1.01 g H/1 mol) = 6.06 g H
molecular weight in grams (representing the
mass of one mole of molecules).
1 mol O (16.00 g O/1 mol) = 16.00 g O
TOTAL = molar mass = 46.08 g/mol
Page 1
Matter can exist as
Atoms, Alloys, Ions, or
Tylenol
Molecules
Some elements exist freely as
atoms in nature:
•Noble Gases
•Metallic Elements
• Formula = C8H9NO2
• Molar mass = ?
Atoms
Atoms
• When metal atoms interact, they delocalize their
electrons to attain a pseudo-octet.
• Electron-Sea Model describes what is known as
metallic bonding:
• Nobel gases actually exist as individual atoms.
 Remember, it is the interactions between the
valence electrons of different elements that
determine how the element will react with other
elements.
• Metals can be thought of
as nuclei with core
electrons suspended in
“sea” of valence
electrons.
• Attractions hold valence
electrons near nucleus,
but not so tightly as to
impede their flow.
• Nobel gases have an octet, therefore, they do
not need to interact with other atoms to be
energetically favorable.
• Metal atoms on the other hand do not have an
octet so multiple atoms must interact to be
energetically favorable.
Matter can exist as Atoms,
Matter can exist as Atoms,
Alloys, Ions, or Molecules
Alloys,
Ions, or Molecules
Metal atoms can exist as evenly distributed
mixtures (homogeneous) known as alloys. Some
alloys contain elements other than metals;
commonly, carbon.
We have seen how metal atoms can “share”
delocalized electrons to achieve a pseudo-octet with
delocalized valence electrons, allowing for a stable
elemental form.
Examples of common alloys are:
However, metals rarely exist as pure
substances. Rather, they exist as ions by completely
giving away their valence electrons. To understand
ions, let us investigate the electron configurations of
some metals.
•Brass (Cu and Zn)
•Steel (Fe, Cr, C)
•Cast Iron (Fe and C)
Page 2
Ions
• A metal atom, such as magnesium, has two valence
electrons.
Ions
• The octet rule states that all atoms seek the electron
configuration of the nearest noble gas, which is for
most elements an octet.
Observe:
12
Mg       
1s
2s
2 px 2 p y
2 pz
3s
• When atoms lose or gain electrons, they become
ions.
• To obtain an octet, magnesium gives up its two
valence electrons to have an octet in the next lowest
energy level.
2
12
 Cations are positive and are formed by elements on the
left side of the periodic chart (metals).
     
Mg
1s
2s
2 px 2 p y
2 pz
• The result is a 2+ charge on the atom
 Anions are negative and are formed by elements on the
right side of the periodic chart (nonmetals).
3s
Charges on Representative Atoms
• Charges on the representative elements can be
predicted by observing their electronegativities and
the electron configuration
• Magnesium becomes to obtain an octet:
12
Mg2
+2
     
1s
2s
2 px 2 p y
-4 -3 -2 -1
+1
+3
2 pz
3s
• Fluorine however is electronegative. So, it is
going to gain an electron to obtain an octet.
9
F
9
F-
    
1s
2s
2 px
2 py
     
1s
2s
2 px
Using a new reference periodic table,
identify the charges for all
representative metals and non-metals
using their group numbers.
2 pz
2 py
Ref.
2 pz
Charges on Transition Metals
Naming Monatomic Ions
• Transition metals can sometimes have more than one
charge. This is due to the movement of electrons
from lower energy levels to higher energy levels,
ultimately changing the number of valence electrons
for the atom.
• Monatomic ions are single atoms that
have gained or lost electrons.
Monatomic cations, formed from metal
atoms are named using the atomic
name
• You will have to memorize the common charges on
the transition metals.
For example:
Na
and
Na+
are both called Sodium
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• Monatomic transition metal cations are
named the same way however, since
transition metals may have more than one
charge, the charge on the metal must be
included in parenthesis using roman
numerals following the name.
• Monatomic anions formed from nonmetals are named using the root of the
atomic name with an –ide suffix
For example:
S2N3-
For example:
Cl-
Fe2+
and
Fe3+
are named Iron (II) and Iron (III)
Are
Sulfide, Nitride, and Chloride.
Not all ions are monatomic. Sometimes a group of
atoms that are bonded together can gain or loose
electrons collectively.
Naming Polyatomic Ions
• The names of polyatomic ions must be
memorized. However, a trend does exist.
Notice, when there are more than one
polyatomic ions that differ only in the
number of oxygens, the ion with the fewer
oxygens has an –ite suffix and the ion with the
greater number of oxygens has an –ate suffix.
The result is a group of bonded atoms with a
charge, known as a polyatomic ion.
There are a large number of polyatomic ions for
which you will need to be able to identify the chemical
formula, charge and name.
Look at your Ion Reference and identify the number of
ions you are responsible for
For Example:
We will eventually learn where polyatomic ions
come from, but for now, all you need to do is be able to
recognize them.
Nitrate vs. Nitrite
Polyatomic Ions
IONIC
COMPOUNDS
NO3nitrate ion
CATION + ANION
--->
IONIC COMPOUND
Na+ + Cl- --> NaCl
A neutral compd.
requires
equal number of +
and – charges held
together by
electrostatic forces.
NO2nitrite ion
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Formula of Ionic Compounds
2 x +3 = +6
3 x -2 = -6
Al2O3
Al3+
1 x +2 = +2
Ca2+
• Name cation, with charge for transition
metal ions in parenthesis, followed by the
anion name.
If the anion is a monatomic anion, use
the anion –ide suffix
If the anion is a polyatomic anion, use
the polyatomic anion name
O22 x -1 = -2
CaBr2
1 x +2 = +2
Na+
Naming Ionic Compounds
Br1 x -2 = -2
Na2CO3
CO32-
To Form Ionic Compounds,
Charges Must Balance
Ca2+ + 2 F- --->
If the difference in electronegativities is
not large enough for one atom to remove
electrons from another atom (ionic bonding),
and they can not “delocalize” their electrons to
obtain an octet (metallic bonding), the atoms
will have to share electrons in order to obtain
an octet.
CaF2
Mg2+ + NO3- ----> Mg(NO3)2
Fe2+ + PO43- ----> Fe3(PO4)2
NH4+ + ClO- ---->
The sharing of electrons in order to
obtain a full valence shell in known as
covalent bonding.
NH4ClO
Non-metals must overlap their atomic
orbitals in order to share electrons with other
non-metals.
Molecular Compounds
Compounds without Ions
1
H
CO2 Carbon dioxide
9
CH4 methane
BCl3 boron trichloride
All are
formed from
two or more
nonmetals.

1s
F     
1s
2s
2 px
2 py
2 pz
Each atom
has an
octet by
sharing
The sharing of an electron pair in
overlapping atomic orbitals known as a
covalent bond.
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Examples of Molecules
Covalent Bond Formation
Aspirin
• A covalent bond can result from an overlap
of atomic orbitals on two neighboring atoms.
••
H
+
••
•
•
Cl
••
Methane
H
•
•
Cl
••
Carbon
dioxide
Overlap of H (1s) and Cl (2p)
Note that each atom has a single,
unpaired electron.
Ammonia
Boron triflouride
Because molecules do not contain ions,
there are no charges to determine the formulas
for the compounds.
Molecular Prefixes:
No Ions !
Therefore, in order to name molecules we
must use prefixes to denote the number of
atoms in a molecular compound.
Naming Molecular
Compounds
1 mono-
6 hexa-
2 di-
7
hepta-
3 tri-
8
octa-
4 tetra-
9
nona-
5 penta-
10 deca-
Lets try naming the following molecules:
•Use prefixes to denote the number of atoms in
the molecule. (mono-, di-, etc…)
1.CCl4
•List atoms in order of increasing
electronegativity
2.Molecule made from 3 sulfur, one
carbon, 2 oxygen and one chlorine
atoms
•The last atom is given an –ide suffix
3.HCH3CO2
•Drop “o” or “a” from prefix for atoms
beginning with a vowel
4.P2S4Br2
Page 6
ELEMENTS THAT EXIST AS
DIATOMIC MOLECULES
ELEMENTS THAT EXIST AS
POLYATOMIC MOLECULES
Allotropes
Allotropes are different
molecular forms of the
same element
Allotropes of C
Oxygen is another
common element
that has allotropes:
O2 elemental Oxygen
O3 ozone
S8 sulfur
White P4 and polymeric
red phosphorus
molecules
-OrFlowers of
Sulfur
Acids and Bases
When we think of acids, we
typically think of the Arrhenius
definition.
Svante Arrhenius (1859-1927)
• Arrhenius Acid = Any compound that increases
the hydronium ion (H3O+) concentration in
aqueous solution
• Arrhenius Base = Any compound that increases
the hydroxide ion concentration in aqueous
solution
MOVIE
Page 7
For any Acid:
For any Base:
HA + H2O → H3O+ (aq) + A- (aq)
Acid + Water → Hydronium + Acid anion
MOH + H2O  M+ + OH- + H2O
The hydrogen of the acid is essentially a single
proton that can bond through a coordination bond to
water forming H3O+, called the hydronium ion.
Water does not always form a
complex for Arrhenius bases as it
does with Arrhenius acids
Examples:
Examples:
HCl(g) + H2O(l) → H3
O+
(aq)
+
Cl-
O
NaOH H→
Na+(aq) + OH-(aq)
(aq)
2
CH3CO2H + H2O ⇄ H3O+ (aq) + CH3CO2- (aq)
O
NH3 + H2O H→
NH4+ (aq) + OH- (aq)
2
•You may notice that polyatomic ions are
formed from some acids or bases, as the acids
or bases loose or gain hydrogen atoms.
For example:
NO3nitrate ion
For example:
• When hydrogen nitrate (HNO3) is placed in
water, H+ and NO3- are formed.
NO3nitrate ion
Hydrogen
nitrate
• It is called hydrogen nitrate as a pure
molecule. However when placed in water, it
is called nitric acid since it produces H+ and
NO3-
Hydrogen nitrate looses a hydrogen proton when placed in
water, resulting in the formation of the nitrate ion (notice the
1- charge)
Naming Acids
An acid is defined as any molecule
that can produce Hydronium ions in
solution.
•Non-Oxyanionic acids = do not contain
oxygen in the resulting anions formed
by the ionization of the molecule
•Oxyanionic acids = contain oxygen in
the resulting anions formed by the
ionization of the molecule.
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