Introduction to Chemical
Bonding
Chemical Reactions:
• During chemical reactions, elements
combine, rearrange, or break apart with
others to form new substances.
• New substances are created when
chemical bonds are broken or created.
New Substance
Original Substance
Chemical Reaction
Magnesium Metal
http://www.polmag.pl/en/media/magnesium.jpg
http://www.bcscience.com/images/m
agnesium_burn.jpg
Magnesium Oxide
http://jchemed.chem.wisc.edu/JCESOFT/CCA/CC
3/STILLS/MAGAIR/MAGAIR/64JPG48/6.JPG
Evidence of Chemical Reactions:
Fire/Burning
Color change without dye
New gas created
Heat released
Heat absorbed
://en.wikipedia.org/wiki/Self-heating_can
tp://static.howstuffworks.com/gif/coldpack.jpg
•
•
•
•
•
http://amazingrust.com/Experiments
/background_knowledge/Images/Fir
e-big.jpg
http://z.about.com/d/chemistry/1
/G/5/a/demonstration.jpg
http://www.uncp.edu/home/mcclurem/pta
Compounds are more than one
kind of element joined together.
Octet Rule: Describes
how chemical bonds
happen.
• Atoms want a full
valence (or outer
electron energy
level).
• Full valence will
mean having 8
valence electrons.
http://www.chemprofessor.com/periodicqm_files/image005.gif
Octet Rule …
Why are these atoms negative?
Gaining electrons (and electrons
•are
Tonegative)
reach means
full valence,
some atoms “want”
more
It is easier
for the to
atom
to
to lose
electrons
and others
“want”
gain
negative
charge
than positive
gain 1, 2 or 3 electrons rather
charges (protons).
electrons.
than losing 5, 6 or 7.
– Atoms with FEWER than 4 valence electrons
will bond by losing those electrons.
• These atoms will become positively charged!
– Atoms with MORE than
valence
electrons
It is 4easier
for the
atom to
will
bond
by gaining
lose
electrons
1, 2 or 3(up
electrons
to eight).
rather
Why are
these
atoms
positive?
than
gaining 5,charged!
6 or 7.
• These atoms will become
negatively
Losing electrons (and electrons
–are
Atoms
withmeans
4 valence electrons can gain or
negative)
lose electrons.
It depends on the element to
more protons
(positive charge)
which
it ischarges.
bonding.
than
negative
Example: Sodium (Na)
• Valence?
1
• Easiest way to follow
Octet Rule?
Lose 1 electron
• If following Octet Rule,
what’s the charge?
+1
http://www.historyforkids.org/scienceforkids/chemistry/atoms/
pictures/sodium.jpg
A chemical bond is created by the sharing or
exchange of electrons between elements.
Example: Fluorine (F)
• Valence?
7
• Easiest way to follow
Octet Rule?
Gain 1 electron
• If following the Octet Rule,
what’s the charge?
–1
http://www.bbc.co.uk/schools/gcsebitesi
ze/science/images/diag_fluorine.gif
What will happen if Sodium and
Fluorine atoms are mixed?
• Electrons could transfer between the
atoms.
• A sodium atom could lose an electron to a
fluorine atom.
• Both atoms are left with full valence & are
bonded together, creating a compound.