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
Why are these atoms negative?
Octet Rule …
Gaining electrons (and electrons
•are
Tonegative)
reach full
valence,
means
more some atoms “want” to
It is
easier for
atom to
lose electrons
others
“want”
tothe
gain
negative
charge thanand
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 thanIt4isvalence
electrons
easier for
the atomwill
to
bond
byatoms
gaining
electrons
(up
to3eight).
lose 1,
2 or
electrons rather
Why are
these
positive?
than gaining
5, 6 or 7.
• These atoms will become negatively
charged!
Losing electrons (and electrons
–are
Atoms
with means
4 valence electrons can gain or lose
negative)
electrons.
It depends
more protons
(positive
charge)on the element to which it
is negative
bonding.charges.
than
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.