1. Test 7: Chemical Bonding
Cartoon courtesy of NearingZero.net

2. Octet Rule
Octet Rule: Atoms will gain, lose, or share valence electrons with other atoms in order to obtain an octet (8 valence electrons).
Exceptions: Hydrogen & Helium – only
2 valence electrons because the
1st PEL holds 2 electrons
In other words, a stable electron configuration.

3. Ions Recall: Atoms are neutral. Why?
An ion is the charged particle formed when a neutral atom loses or gains electrons.
If an atom gains electrons, it becomes a NEGATIVELY charged ion.
If an atom loses electrons, it becomes a POSITIVELY charged ion.

4. Metal Ions
Metals tend to lose electrons and form smaller sized ions that are positively charged.
Atom Ion

5. Nonmetal Ions
Nonmetals tend to gain electrons and form larger sized ions that are negatively charged.
Atom Ion

6. Why?
Metals generally have 1, 2, or 3 valence electrons. For metals it is easier to lose those than gain 5,6,or 7 additional electrons.
Nonmetals generally have 5, 6, or 7 valence electrons. For nonmetals it is easier to gain 1, 2, or 3 more electrons than to lose 5, 6, or 7 electrons.
They want the electron configuration of the Noble Gas closest to their atomic number.

7. Ion Charges
Possible ion charges are listed as oxidation numbers on the PT
Example: aluminum ion = 3+
oxygen ion = 2-
chloride ion = 1-

8. Bonding Chemical bonds are attractive forces that hold atoms together.
2. Compounds – 2 or more different atoms chemically bonded together
ex: NaCl or H2O
3. Diatomic Elements – 2 of the same atoms bonded together
ex: H2 O2 F2 Br2 I2 N2 Cl2

9. Hey! I find your electrons attractive!
Electronegativity
(attraction for another atom’s electrons)
Get lost, loser!
Hey! I find your electrons attractive!

10. Electronegativity – Table S
Metals – Low #’s Nonmetals – Big #’s
low attraction big attraction
Think
Metals lose e- & form + ions
Nonmetals gain e- & form - ions

11. (less than 1.7 but more than zero)
Chart to Memorize!
Type of Bond
Ionic
Polar Covalent
Nonpolar Covalent
Electronegativity Difference…
>1.7
(equal to or more than 1.7)
1.7>x>0
(less than 1.7 but more than zero)
= zero
Valence Electrons are…
Transferred
Shared unequally
Shared Equally
How to Recognize…
Metal & Nonmetal
2 Different Nonmetals
2 of the same Nonmetals
Chemical Formula for one example…
NaCl
H2O H2

12. Electronegativity Chart
To Determine Electronegativity Difference for CaBr2:
Br = 3.0
Ca = 1.3
Difference is 1.7
So CaBr2 Bond is Ionic