10/27/15 The Octet
Rule
October 27th, 2015
The Octet Rule
10/27/15
›  Objective:
›  Define
›  DO
and apply the octet rule
NOW
›  Determine
the number of valence electrons for the
following elements:
§ Al
§ Li
§ Ca
§ Mg
§ K
§ N
§ C
§ B
§ O
§ Xe
1 10/27/15 ›  DO
NOW
›  Determine
the number of valence electrons for the
following elements:
§ Al-3
§ Li-1
§ Ca-2
§ Mg-2
§ K-1
§ N-5
§ C-4
§ B-3
§ O-6
§ Xe-8
Valence Electrons
›  Review:
1. 
What are valence electrons?
2. 
What are their purpose?
3. 
How do we find them?
2 10/27/15 Valence Electrons
›  Review:
Answers
What are valence electrons?
Outermost electrons or electrons in the outermost
energy level.
1.  What are their purpose?
Bonding! (Lose, gain, and share valence electrons to
form bonds.
1.  How do we find them?
Look at the column number on the periodic table!
1. 
Determining the # of Valence Electrons Using the Periodic Table
1
2
3
4
5
6
8
7
3 10/27/15 The Octet Rule
› The
octet rule states that atoms will lose,
gain, or share electrons in order to achieve
a full valence shell
›  Full
valence shell = full outermost energy
level
› For
most* atoms, this means they want to
achieve an octet, or have 8 valence
electrons
Applying The Octet Rule
› When
an atom achieves a full octet,
it is very stable
› What happens when atoms lose or
gain electrons?
4 10/27/15 Ionic Charges
›  When
ions
atoms lose or gain electrons, they will form
›  Positive
ion = cation
›  Negative ion = anion
›  Based
on the number of valence electrons an
atom has and the octet rule, you can predict the
charge an atom is likely to form!
Determining the # of Valence Electrons Using the Periodic Table
+1
+2
+3 N/A -3
N/A
-2 -1
5