Catalyst – March Uno, 2010
Monday Mystery Element!
1.
2.
3.
A “p-block” element
Name is Latin for
“violet”
When bent, makes a
shrieking noise
Catalyst – March Uno, 2010
Monday Mystery Element!
1.
2.
3.
A “p-block” element
Name is Latin for
“violet”
When bent, makes a
shrieking noise
INDIUM!
Today’s Agenda
Catalyst
 Lewis Dot Structures
 Stable Ions
 Octet Rule
 Work Time…Oooh Oooh!
 Exit Question

Today’s Objectives
SWBAT draw Lewis Dot Structures
for atoms and ions.
 SWBAT determine the charge on an
ion.
 SWBAT use the octet rule to predict
the number of electrons in a stable
ion.

Valence Electrons Review

Electrons in the outermost level or
shell of the atom that determine the
chemical reactivity of an element
Outer
s and p electrons
These electrons are involved in
bonding
Valence Electrons

Valence electrons are the
electrons in the outside energy
level
ALL TOGETHER, SODIUM HAS 11
ELECTRONS.
NUCLEUS
SODIUM HAS 1
VALENCE ELECTRON
P=11
N=12
What is a compound?
Key Point #1: A compound results
from interaction between valence
electrons of different atoms.
Chemical Bond Spotlight: NaCl (table salt)
Na
Cl
NaCl
2 different elements:
 Sodium (Na)
 Chlorine (Cl)
1 compound:
 Sodium chloride
(NaCl)
Chemical Bond Spotlight: NaCl (table salt)
Let’s see
a video!
Lewis Dot Structures
Key Point #2: Lewis Dot Structures
only show the number of valence
electrons in an atom.


Valence electrons are the only electrons
involved in bonding
Valence electrons are the most
important electrons
Drawing Lewis Dot Structures
Write element symbol.
2. Determine number of valence
electrons.
3. Place single dot on right side and
add single dots counterclockwise.
EXAMPLES COMING UP…
1.
Count ve-…then draw LDS
1.
2.
3.
Boron
Oxygen
Lithium
LDS Example 1: Sodium (Na)
1.
2.
3.
Write element symbol.
Determine number of valence
electrons.
Place single dot on right side and
add single dots counterclockwise.
LDS Example 2: Neon (Ne)
1.
2.
3.
Write element symbol.
Determine number of valence
electrons.
Place single dot on right side and
add single dots counterclockwise.
Lewis Dot Sructures
What do the
Lewis Dot
Structures have
in common?!?!?
I have a few QUESTIONS…
1.
What kind of charge does an electron have?
•
2.
(-1)
What kind of charge does an entire atom
have?
•
Neutral (as many positives as negatives)
So….if an atom gains an electron what kind
of charge will it have?
What about if an atom loses an electron???
First thing you need to know about
ionic bonds….

Key Point #3: An ion is an element
that has gained or lost an electron.
Cation = positive ion (+)
Anion = negative ion (-)
-
+
Types of ions
Cation – a positive ion (+)
“t” looks like (+)
Anion – a negative ion (-)
“n” or onion for negative

Formation of Negative Ions (ANIONS)



Again, imagine that electrons
are pieces of poop
Is poop is flying into your yard
(an atom’s energy levels) a
positive or negative thing?
So…if poop lands in your
yard, are you more positive or
more negative?
-
So…NEGATIVE ions are formed when an
atom GAINS one or more electrons!
Formation of Positive Ions (CATIONS)



Imagine that electrons are
pieces of poop
Is poop in your yard (an atom’s
energy levels) a positive or
negative thing?
So…if you get rid of the poop
in your yard, are you more
positive or more negative?
So…POSITIVE ions are formed when an
atom LOSES one or more electrons!
+
Practice Questions
1.
2.
3.
If an atom gains an electron it will have
NEGATIVE charge.
a ___________
If an atom loses an electron it will have
a ___________
charge.
POSITIVE
If chlorine gains 3 electrons it will have
a _______
charge.
3-
Ions!
Cl loses 4
Electrons
What is the stable ion?
Ions!
Cobalt gains
2 electrons
What is the stable ion?
Ions!
3Si
What happened…
gain or lose…
how many?
Ions
3Si
Silicon gains 3 electrons
How many total electrons
does Si have now?
Practice Problems – Write all down!

Write down the stable ion that will
form for the following:
1.
2.

Sr gains 5 electrons
Phosphorous loses 1 electron
Then, answer how many electrons
TOTAL will they have now?
Practice Problems – Write all down!
How many TOTAL electrons do the
following ions have?
2+
1. Cl
22. Li
3+
3. Xe
14. O
55. Zn
Octet Rule
What is different
about the valence
shells of the elements
on the Left and those
on the Right?
 The noble gases have
full valence shells, the
other atoms do not…

Octet Rule – Elements
are most stable when
they have the electron
configuration of a noble
gas (Key Point next…)
Octet Rule
Key Point #4: The octet rule says that atoms
are most stable when they have 8 valence
electrons.
1. Atoms can gain or lose electrons to become
stable (happy) 
2. Atoms with 4 or more valence electrons will
GAIN electrons to become stable (happy) 
3. Atoms with 3 or less valence electrons will
LOSE electrons to be stable (happy) 
Octet Rule - Examples

How many electrons will the following atoms
gain or lose to become stable (happy)? How
many TOTAL electrons will the atom then
have? What is the STABLE ION?
1.
2.
3.
4.
F
O
N
H
Try the following on your own

How many electrons will the following atoms
gain or lose to become stable (happy)?
How many TOTAL electrons will the atom
then have? What is the STABLE ION?
1. P
2. Kr
3. Ca
4. I
5. K
Worksheet for Class or HW
Half Shee – eet!
Take care of your
bidness and complete
it tonight!
Exit Question
1.
2.
Anion = _______ charge, Cation = _______ charge
What is the STABLE ION that will form for the following
elements? Write down the ion and how many electrons
the atom will have TOTAL.


4.
Te
Li
Draw the LDS for the following elements:


Sulfur
Magnesium