Ions
Valence Shell
• The outer ring of an atom filled with valence
electrons
Octet Rule
• Atoms are most stable when they have a full
octet, or 8 valence electrons
• Some atoms are exceptions – they are most
stable with only 2 electrons (H, He, Li, Be, B)
• Noble gases are all stable
Anions
• Some atoms GAIN electrons to become stable
• Negative charge
Anion Charge
• If chlorine gains an electron…
P: 17+
E: 18Overall charge: -1
Cations
• Some atoms LOSE electrons to become stable
• Positive charge
Cation Charge
• If sodium loses an electron…
P: 11+
E: 10Overall charge: +1
Bohr Model
• Complete the following Bohr models.
• Determine if the element needs to lose or gain
electrons to become stable
• (remember the levels!)
K
Mg
O
F
Ne
Patterns with valence electrons
• What patterns do you notice based on your
Bohr models?
• The number of valence electrons matches the
group number
Oxidation Number
• The number of electrons needed to gain or lose
for stability equals the oxidation number, or
charge
• Also a pattern by group
• Label these representative groups:
• Group 1: +1
Group 5: -3
• Group 2: +2
Group 6: -2
• Group 3: +3
Group 7: -1
• Group 4: none
Group 8: none
Ion P, N, E
Symbol
Protons
Neutrons Electrons Charge
K+1
19
20
Be+2
Al+3
P-3
S-2
I-1
Xe
18
+1
Lewis Dot Structures
• Used to represent the number of valence
electrons
• Can be used later in symbolizing chemical
bonds between atoms
Checkpoint
1. Why do atoms gain or lose valence electrons?
2. Describe the change in an atom that has a +3
charge. Why is it positive? What does the “3”
mean?
3. When atoms gain or lose electrons, where do
they go?
4. Define the octet rule.
5. Describe the patterns seen on the periodic table
related to electrons.