Atoms that interact to form
compounds are said to be
chemically bonded.
Whether atoms interact
depends almost entirely
on the arrangement of
their outer energy
level (valence)
electrons.
Only s and p sublevel
electrons are thought
of as valence
electrons.
The maximum number
of electrons, total, in the
s and p sublevels is __
The maximum number
of electrons, total, in the
s and p sublevels is 8.
Electrons in the d and f
sublevels are NEVER
in the outer energy
level of an atom.
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Bonding - 7 min
Electrons are transferred
between atoms.
One atom gains electrons
while another atom
loses electrons.
When this happens, the
charges within each atom
are no longer balanced...
the atoms have become
ions - one with a positive
charge, the other negative.
The force of attraction
between these opposite
charges hold the ions
together in an ionic bond.
Ionization - the process of
removing an electron from
an atom to form an ion.
Ionization energy - the
energy needed to remove
an electron from an atom.
Electron affinity - the
tendency of an atom
to attract electrons.
Electron affinity
determines the
type of bond formed.
Metals generally have
a low electron affinity.
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Nonmetals generally have
a high electron affinity.
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Electrons are shared
between atoms.
Atoms with similar
electron affinities usually
form covalent bonds.
Both atoms have an
equal attraction for the
electrons being shared.
The force of attraction between
the nuclei and the shared
electrons holds the atoms
together in a covalent bond.
Chemical bonds are
almost never totally ionic
or totally covalent.
Bond types are often
expressed as a
percentage of each
type of bond.
CO
and
CO2
The closer two
atoms are on
the table, the
more covalent
their bond.
NaCl
The farther apart
two atoms are
on the table, the
more ionic
their bond.
100%
Ionic
100%
Covalent
FrF
F2
ZnS
50% Each
The electrons in metals
can be thought of as being
property of all the atoms.
The positive nuclei are
surrounded by a "sea"
of electrons.
These loosely-held electrons
are responsible for metals
being good conductors
of electricity.
A special type of bond
between a hydrogen atom
in a covalent molecule...
and an unshared electron
in a nearby molecule.
Since a hydrogen atom is
so small, it can get very
close to other atoms -
causing electrons in those
atoms to be attracted to it.
This is especially
important with small,
polar molecules
like water.
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It makes water a VERY
GOOD solvent especially with other
polar substances.
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Hydrogen bonding is
responsible for water's
very high specific heat
capacity...
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the ability to absorb
large amounts of heat
with little change
in temperature...
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and its relatively
high boiling point.
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two atoms of the same
element covalently
bonded together.
Seven elements exist in nature
ONLY as diatomic molecules.
Know the seven
diatomic molecules!!
Hydrogen - H2
Nitrogen - N2
Oxygen - O2
Fluorine - F2
Chlorine - Cl2
Bromine - Br2
Iodine - I2
Begin with #7
There are 6 here
in the shape of a 7
And 1 more here
A group of covalently
bonded atoms that has
an overall charge.
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This group of atoms
acts like a single ion
when combining to
form compounds.
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The charge on a
polyatomic ion is
equal to its
oxidation number.
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Certain electron
arrangements are more
stable than others.
The most stable atoms
have a full outer
energy level.
Octet Rule - the maximum
number of electrons in the
outer energy level is 8.
Atoms will form compounds
to reach eight electrons in
their outer energy level.
Remember - hydrogen &
helium, with only one
energy level, can only
hold 2 electrons.
Atoms with half-filled
sublevels are somewhat
stable.
A way of
drawing the
valence
electrons.
p
p
s
p
The chemical symbol
p
represents the
center of an
p
imaginary
rectangle.
p
s
The symbol represents the
atom's nucleus and p
all electrons,
p
s
EXCEPT the
valence
p
electrons.
Each side of the imaginary
rectangle
p
represents an
p
s
orbital within
a sublevel of the
outer energy level p
Valence electrons in
each orbital are p
represented
p
by dots.
p
s
These arrows show the order
in which electrons p
are added to the
diagram p
s
beginning
with s.
p
The electron dot diagram
for sodium looks
like this Na
with one electron
in the s orbital.
What would the electron
dot diagram for
magnesium
look like?
What would the electron
dot diagram for
magnesium
Mg
look like?
What would the electron
dot diagram for
Aluminum
look like?
What would the electron
dot diagram for
Aluminum
Al
look like?
What would the electron
dot diagram for
Silicon
look like?
Hint: Remember Hund's Rule
What would the electron
dot diagram for
Silicon
Si
look like?
What would the electron
dot diagram for
Phosphorus
look like?
What would the electron
dot diagram for
Phosphorus
P
look like?
What can you say about
the stability of
an atom of
P
phosphorus?
An atom of phosphorus
is somewhat stable
because of
P
the half-filled
p sublevel.
What would the electron
dot diagram for
Sulfur
look like?
What would the electron
dot diagram for
Sulfur
S
look like?
What would the electron
dot diagram for
Chlorine
look like?
What would the electron
dot diagram for
Chlorine
Cl
look like?
What would the electron
dot diagram for
Argon
look like?
What would the electron
dot diagram for
Argon
Ar
look like?
What can you say about
the stability of
an atom of
Ar
argon?
An atom of argon is
very stable because
its outer energy
Ar
level is full.
What would the electron
dot diagram for
Copper
look like?
What would the electron
dot diagram for
Copper
Cu
look like?
All transition metals
have only two dots Why?
Cu
Notice the number of
dots is the same as
the group number.
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Also notice that these
dots are not placed
exactly as we discussed.
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Many college chem books
stress symmetry of dots
more than sublevels.
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Since THIS class stresses
the periodic table,
sublevels are important.
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What do you think of?
H
H
O
Can these 3 atom diagrams
H
H
O
be combined into
1 molecule diagram?
A
Water
Molecule
H2O
O
H
All atoms have a filled
outer energy level.
This diagram not only shows
properly filled
energy levels,
it correctly
shows the shape
of a water molecule!!
O
H
Hypothesis:
When 10 cm3 of acetone, C3H6O,
are added to 10 cm3 of distilled water,
the combined volume is NOT 20 cm3.
Chemical Bonding
Test Tomorrow
Whether atoms interact
depends almost entirely
on the arrangement of
their _____ electrons.
Only ___ and ___ sublevel
electrons can be valence
electrons.
_____ bonds occur when
electrons are transferred
between atoms.
When atoms gain or
loose electrons, they
become ____.
The tendency of an atom
to attract electrons
is called ____.
Atoms with similar
electron affinities usually
form ____ bonds.
Bonding is usually
expressed as a ___ of
each type of bond.
There are ___
diatomic molecules.
Diatomic molecules must
be written with a
subscript of ___.
A group of covalently
bonded atoms with
an overall charge is
called a ___.
In an electron dot diagram,
dots represent ___.
The ___ states that
the maximum number
of electrons in the
outer energy level is 8.
The valence electrons in
the atoms of a sample of
metal belong to ___.
The oxidation number of
a polyatomic ion is
equal to its ___.
Which of these atoms is
most likely to form an
ionic bond with sulfur?
Lithium, nitrogen, aluminum
Which of these atoms has
the highest electron affinity?
Lithium, sodium, carbon
Which of these atoms will
form a negative ion?
iron, tin, chlorine
How many dots are in the
electron dot diagram
of arsenic?
How many dots are in the
electron dot diagram
of mercury?
Which of these atoms
is the most stable?
iron, nitrogen, chlorine
How many of these atoms
do not conform to the
octet rule?
hydrogen, helium, argon
The formula for the
phosphate ion is ___.
The formula for the
ammonium ion is ___.
The formula for the
sulfate ion is ___.
Chemical Bonding