Transcript Covalent Bonds

Covalent Bonds
By Wendy Bradley
Acacia Dunphy
Andrew Hudson
Kaitlyn Tanner
Properties of covalent
compounds
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A single covalent bond is formed when a pair
of electrons is shared between two atoms
Usually have lower melting points and boiling
points
They are more flammable than ionic
compounds
They don’t conduct electricity
Usually aren’t soluble in water.
There are two kinds of covalent bonds; polar
and non-polar (pure) covalent bonds.
Electronegativity
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The tendency of an atom to draw or attract
the electrons in a bond toward itself.
To form a covalent bond, two or more atoms
with similar electronegativities will share
electrons
Electronegativity is like a game of tug-of-war
with a puppy. An atom's ability to pull
determines what kind of bond it forms.
Electronegativity Trends
Lewis Structure
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Also known as electron-dot diagram, which is
a simple diagram showing the valence
electrons as dots.
Some diagrams show the bonding between
different atoms
Gilbert N. Lewis came up with the idea of the
octet rule, which is that atoms react by
changing the number of their electrons, so as
to acquire the stable electron structure of a
noble gas.
Resonances
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Occurs when two or more equally valid electron dot
diagram can be written for a molecule
Earlier chemists thought that the electron pairs were
rapidly flipping back and forth or resonating between
the various electron dot diagrams
But more recently we have found that electron pairs
do not resonate. The actual resonance bonding is
considered to be hybrid or a mixture of the extremes
represented by the resonance forms.
Used to represent certain types of molecular
structures
A very important part in the valence bond theory
Polar covalent compounds
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When two different atoms are joined by a
covalent bond and the bonding electrons are
shared unequally.
Also called ‘Polar Bond’ for short
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Page 336 and 324 in the white/green book
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Interactive Bonding Lab
Each of the following activities is done in groups of 2-3 people.
Purpose: to be able to visualize bonding, angles, multiple bonds, as
well as the position of lone pairs in molecular formulas.
Materials: Large Marshmallows, small colored marshmallows, red-hot
candies, gumdrops, and toothpicks
Compounds involved:
H2O-Water
CH4--Methane
C2H4-Ethane
N2-Diatomic Nitrogen
CH2O-Formaldehyde
NH3-Ammonia
Procedure:
Make Water Molecule
O-large marshmallow
H-small marshmallow
Lone pair-red-hot candies
Make Diatomic Nitrogen Molecule
N-Large Marshmallows
Lone Pairs-Red-hot candies
Make Formaldehyde Molecule
C-Large Marshmallow
H-Small Marshmallows
O-Large Gumdrop
Red-hot candies if needed
***Remember to use more toothpicks if multiple bonds occur.
Across
3. These special electrons are found in the
outer most shell of an atom
5. _____ bonds are bonds formed when
two different atoms are joined by
covalent bond and the bonding
electrons are shared equally
6. All atoms want to be happy or ______
8. Gilbert N. Lewis came up with the
_______ rule
9. A substance that can be separated into
simpler substances (elements or other
compounds) only by chemical
reactions
10. The force between electrons and
protons
11. When two or more electron-dot
diagrams can be written for a molecule
Down
1. The tendency of an atom to draw or
attract the electrons in a bond toward
itself
2. ____________ bonds
4. Also known as the electron-dot diagram
5. A non-polar covalent compound
7. _________ you will find in orbitals