FORMING COMPOUNDS DAY 2
IONIC BONDS
IONS
•Ion: an atom gains or loses electrons
Two types:
•Anions: Atoms that gain electrons.
Anions
have a NEGATIVE charge
•Cations: atoms that lose electrons.
Cations have a POSITIVE charge
Why would atoms gain or
lose electrons?
Full valence shell = Stable atom
• Atoms that do not have a full valence
shell are considered unstable
• Atoms will try to gain or lose electrons to
have a full valence shell and become
stable
.
Na
Examples
+
Na
cation
Examples
__
Cl
Cl
Anion
How do you determine whether an
element is a Cation or Anion?
•Elements
in groups 1, 2, and 3 will
form cations (lose electrons)
•Elements in group 4 can form both
cations and anions depending on its
partner element
•Elements in groups 5, 6, or 7will form
anions (gain electrons)
So how does this look?
•If O gains two electrons it would have a
full valence shell and become an anion
O → O²¯
•If B loses three electrons, it would have a
full valence shell and become a cation
B→
3
B⁺
You try it…
For the following atoms, how many electrons need
to be gained or lost to have a full valence shell:
Element
name
F
Does it gain or
lose electrons?
How many valence
electrons?
Ion symbol
K
Al
S
Be
N
Now write them in their ion form (ex. O2-)
Why is this important?
•Elements want to have a full valence shell to
become stable and will Bond to make this
happen
Remember valence electrons determine
an element’s chemical properties.
•
Elemental Bonding
An Ionic Bond is a chemical bond where an
atom will gain or lose valence electrons to have
a full valence shell.
Happens between metals and non-metals
ONLY
Na
Cl
Na
Cl
Ionic Bonding Rule
1.Draw the lewis dot diagram of each element
2.Determine the Anion and Cation
3.Draw the electron transfer using arrows
4.Write out the end result with charges
Ionic bonds can be straightforward
Al
P
Al
P
3+
Al
3P
Ionic Bonds may not be straightforward
Li + O
Li
O
Li
O
Oxygen’s Valence shell is not full. Any ides
what we could do?
Add another Lithium to the equation!
Li
Li
O
Li
Li
O
Li2
1+
2O
The #2 below an element
indicates that you used 2
of them
Independent practice
Complete Ionic Bonding
Worksheet
Due: End of Class