Transcript Bonds The eternal mystery of the world is its comprehensibility - Albert Einstein

Bonds
The eternal mystery of the world is its
comprehensibility
- Albert Einstein
Chemical
Bonds
• Chemical compounds
are formed by the
joining of two or more
atoms.
• This point of union is
called a bond.
• The bond means there
is an attractive force
between the atoms.
• Bonds are more like
springs then sticks.
Some atom movement
is possible.
• There are 3 main types
of bonds, Ionic,
• Ionic bonds are formed
by a transfer of
electrons.
• One of the atoms gains
the electron(s) that the
other lost.
• Both end up with full outer
energy levels and opposite
charges.
• The oppositely charged
ions are attracted to each
other.
• Many ions bond together
forming networks.
• This is shown in the
diagram of NaCl to the
right.
• In the diagram, Na is red
and Cl is green.
Ionic Bonds
Ionic Bonds
• Ionic bonds are formed
by a transfer of
electrons.
• One of the atoms gains
the electron(s) that the
other lost.
• Both end up with full
outer energy levels and
opposite charges.
• Electric current is
moving charges.
• Solid ionic compounds
do not conduct
electricity because the
charged ions are
locked in place.
• When dissolved, ionic
compounds
disassociate or
separate into their
ions.
• The solution can now
conduct electricity
because the ions are
free to move.
• A solid block of salt
and a beaker of
distilled water will not
conduct electricity, but
a beaker of salty water
will!
Ionic compounds and conduction
Metallic Bonds
• The attraction between a
metal atom’s nucleus and a
neighboring atoms electrons
is strong and packs the
atoms closely together.
• This causes the outermost
energy levels of the atoms to
overlap.
• These outermost electrons
are free to move from atom
to atom.
• This explains why metals are
good conductors and why
they are so flexible and
malleable when compared to
the non-metals.
Covalent Bonds
• A covalent bond
forms when two or
more atoms share
valence electrons.
• This occurs most
often between
elements in groups
IVA, VA, VIA and
VIIA.
• The sharing of
electrons allows
each atom in the
molecule to have a
stable octet in its
outermost energy
level.
• The methane
molecule illustrated
has 4 covalent
bonds.
• The bonds are
between each
hydrogen atom and
the carbon atom.
• The sharing of
electrons means
sometimes they are
going around the
carbon and
sometimes they are
going around the
hydrogens.
• In this way each
element gets to have
a full outer energy
Methane (CH4)
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The shared electrons in
a covalent bond may not
be shared equally.
Electrons are strongly
attracted to atoms
located to the upper right
of the periodic table.
In the water molecule,
the oxygen atom has a
much stronger
attraction for the
electrons then either
hydrogen.
This means that the
electrons from the two
hydrogens spend most of
their time orbiting the
oxygen atom.
Because of this unequal
sharing a molecule of
water has a negative and
a positive end (poles).
Polar Covalent bonds
Water is Special!
• Because of the
polar nature of the
water molecule it is
attracted to itself!
• Water molecules
are attracted to
each other and this
is the main reason
that such a small
molecule is a liquid
at room
temperature!
Many water molecules showing hydrogen bonding
Ice Structure - note similarities
to snowflakes!
Glacial Blue ice - ice that is formed by the recrystallization of snow that is
compacted in a glacier.
Huge tabular iceberg from Antarctica
Blue ice berg,
Antarctica
Carbon dioxide, polar covalent but with a twist!
• In the CO2 molecule
the oxygen atoms
have the electrons
more often than the
carbon atoms.
• This makes the
oxygen ends of the
molecule negative and
the area between the
oxygen and the
carbon positive.
• How does this explain
the fact the CO2 is a
gas at room
temperature even
Dry Ice
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Dry ice is the solid form of the
gas carbon dioxide.
A full block, measuring about 10
inches square, weighs 50 lbs.
The temperature of dry ice is
110° below zero.
When handling dry ice, wear
work gloves as the extremely
low temperature will cause
frostbite.
Dry ice has many uses, chief
among them as a refrigerant to
prevent food form perishing and
to ship blood products.