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The valence electrons in an atom have
HIGH POTENTIAL ENERGY
By bonding with other atoms, potential
energy is decreased creating stable
compounds.
Symbols of atoms with dots to represent the
valence-shell electrons.
(The valence- are the e- directly involved in bonding).
Ar
Mg
C
The Noble Gases do not react with other
elements because they are already
STABLE.
The outer most “s” and “p” orbitals are completely filled with 8
electrons, satisfying the octet rule.
Ne
Elements combine with each other to achieve
noble gas electron configurations
or
(8 outer e-)
**The exceptions to the octet rule are
Hydrogen and Helium
(they only need 2)
•
The forming of chemical compounds results
in chemical change.
•
Compounds are made up of chemically
united elements
Compounds have completely different
characteristics than its component elements
•
•
Compounds are NEUTRAL
2H2O = H2O = HHO
H2O HHO
Subscript = # of atoms
Coefficient = # of molecules
N: 1
H: 5
O: 1
The Gaining and Losing of Electrons
to form IONS.
(An ion is an atom with a charge.)
sharing of electrons
•
•
•
•
Soluble in water
Do not transmit electric current
Brittle
High melting and boiling points
Ionization Energy: the amount of energy
needed to remove an e- from an atom.
Metals
have a low
ionization
energy
Nonmetals
have high
ionization
energy
because
they are
closer to
satisfying
the octet
rule!
the higher the electronegativity the greater the
ability to pull electron to itself
The nature of a bond is determined by differences in electronegativity.
The GREATER the electronegativity difference, the MORE ionic the bonding.
Ionic compounds result when metals react with
nonmetals
Metals lose electrons to achieve a stable outer energy
level
• Positive ions form when electrons are given away
•
Group 1 metals  ion 1+
Group 2 metals  ion 2+
Group 13 metals  ion 3+
1. Write the symbol for the cation (+) followed by the
symbol for the anion (-).
2. Put any polyatomic ions (see green boxes) in
parenthesis
3. Write the oxidation numbers above the appropriate
ions
4. Use the criss-cross method to deterimine # of
atoms (do not criss-cross ones)
5. Make sure the sum of all ox# is ZERO.
6. Reduce
Sodium
Atom
Sodium
Ion
Na 
11 p+
11 e0
– e


Na +
11 p+
10 e1+
Fluoride
Atom
Fluoride
Ion
+ e
17 p+
17 e0

1-
17 p+
18e1-
Na 
+

1+
Na
1-
YOUR TURN…
Using dot diagrams, draw the Lewis structures that result when the
following elements form ionic bonds:
A. Potassium + chlorine
B. Magnesium + fluorine
Potassium + Chlorine
K
Cl
+
K
Cl
Magnesium + Fluorine
Mg
+
F
Mg
F
Oxidation: the process of losing electrons
▪ Creates an ion with a + charge
▪ Creates cations
Reduction: the process of gaining electrons
▪ Creates an ion with a – charge
▪ Creates anions
1. Write the name of the cation (+)
2. Write the name of the anion (-) with an ide suffix
NaCl
Sodium and Chlorine
Sodium Chloride
The oxidation number is not always the same, it
varies.
The variable oxidation states are represented with a
roman numeral in parentheses and are located in
groups
3-12 on the periodic chart.
Copper
Copper (I) = Cu+ Copper (II) = Cu2+



Write the symbol for the cation followed by
the symbol for the anion.
Write the oxidation numbers above the
appropriate ions.
Criss-Cross
3+
2-
Copper(III) Oxide: CuO Cu2O3
1+ 2-
Copper(I) Oxide: CuO Cu2O
SO4
C2H302
NO3
NO2
NH4
HCO3
CO3
OH
ClO3
PO4
Sulfate
Acetate
Nitrate
Nitrite
Ammonium
Bicarbonate
Carbonate
Hydroxide
Chlorate
Phosphate
21111+
12113-
1. Write the name of the cation (+)
2. Write the name of the anion (-)
3. If either is a polyatomic ion write the name of the
polyatomic ion (you don’t need to change any
suffixes)
Na(OH)
Sodium Hydroxide
Write the symbol for the cation followed by the symbol
for the anion.
 Put all polyatomic ions in parentheses!!
 Write the oxidation numbers above the appropriate
ions.
 Criss-Cross

2+
3-
1+
3-
Calcium Phosphate: Ca(PO4)
Ammonium Phosphate: (NH4)(PO4)
Ca3(PO4)2
(NH4)3(PO4)
1+
1-
=0
Cu(OH)
3+
62-
Ni2O3
Copper (I) Hydroxide
=0
Nickel (III) Oxide
sharing of electrons




Between nonmetallic elements of similar
electronegativity.
Formed by sharing electron pairs
Stable non-ionizing particles, they are not
conductors at any state
Examples; O2, CO2, C2H6, H2O, SiC
Water is a polar molecule because oxygen is more electronegative than hydrogen,
and therefore electrons are pulled closer to oxygen.

A polar molecule has a (+) and a (-) end.

A nonpolar molecule does not have charged ends.
Metal + Nonmetal --> ionic compound
(usually)
Metal + Polyatomic ion —> ionic compound
(usually)
Nonmetal + Nonmetal —> covalent compound
(usually)
Hydrogen + Nonmetal —> covalent compound
(usually)

The chemical symbol for the atom is
surrounded by a number of dots
corresponding to the number of valence
electrons
1. Write the name of the cation (+) with
appropriate prefix (do NOT use mono for the
cation)
2. Write the name of the anion (-) with the
appropriate prefix
CO2
Carbon Dioxide
1:
2:
3:
4:
5:
6:
mono
di
tri
tetra
penta
hexa



Formula weight is the sum of the atomic
masses.
Example- CO2
Mass, C + O + O
12.011 + 15.994 + 15.994
43.999