Classic
Chem
If I wanted
to bond,
could I?
9-12 Science Std: Chem 2a
Previously, on “Chem is Fun”
Review from beginning:
Started with Atom
The parts
The
electrical
charges
The orbitals
Valence Electrons
Previously, on “Chem is Fun”
Review from beginning:
Valence
electrons
Outer shell…
Electrons that
bond….
electron
neutron
proton
Previously, on “Chem is Fun”
Review from beginning:
How many there
are….
1
2
Count from left…
Working with table…
3
4
5
6
7
Or look at column number
8
Previously, on “Chem is Fun”
Review from beginning:
Sharing
electrons
Covalent, Polar Covalent and Metallic
Previously, on “Chem is Fun”
Review from beginning:
Taking / Giving Electrons
Ionic Bonds held by Electrostatic Forces
Not all atoms can bond
It depends on the number of valence electrons
Imagine if you will…..
…..An apartment building
This building has 8 apartments / floor
“Eight is Great”
Not all atoms can bond
Each floor of the apartment is an element or atom
Valence
electrons live in
the apartments….
The Number of full or
empty “apartments”….
…is important to the
“landlord” atom
Not all atoms can bond
When atoms bond…
Atoms work
together to
move electrons
from “apartment”
to “apartment”
So that each atom
has either…
…an empty or
full floor
Not all atoms can bond
When atoms bond…
If they can’t fill
or empty a floor
The atoms don’t want
to bond
Here’s how it works….
An atom with 2 valence
electrons
Wants to Bond with an atom
with 6 valence electrons
Atoms aren’t happy – floors aren’t
empty or full
Here’s how it works….
This atom takes its
electrons
And moves them to the
other atom
Now both atoms are happy and can bond
Here’s how it works….
This is called the “rule
of eight”
Or the “Octet Rule”
Remember – “Eight is Great”
Here’s how it works….
If the atom can’t fill or
empty the
floor…
The Octet Rule isn’t
followed…
And the atoms don’t want to bond
Here’s an example
An atom with 3 valence
electrons
Comes near an atom
with 5 valence electrons
Will these atoms bond?
Here’s an example
This atom moves its 3
electrons
Yes!
Into the 3 empty places
in this atom
And the atoms will get together and bond
Another example:
An atom with 2 valence
electrons
Sees an atom with 5
valence electrons
Will these atoms bond?
How could they bond?
Move the electrons and
this atom
is happy…
Where could they
get it?
But this atom still needs
one for the Octet Rule
A 3rd Atom with one
electron
Bonds with more than 2 atoms
You bring in a 3rd atom
with 1 valence electron
And both atoms move
their electrons
Now all 3 atoms have met the Octet Rule
And all 3 atoms will bond together!
Does this work the other way?
Will an atom with 5
valence
electrons
Move those 5 to an
atom with only 3?
It is easier to move 3 electrons than 5
No – 3 electrons will move to the atom with 5
How about this one…
You have an atom with
4 valence electrons..
It wants to meet the Octet
Rule to be happy
So it looks for atoms to bond with
How about this one…
It sees 2 other atoms
with 2 valence
electrons
Will it bond with these 2
atoms?
Yes!
The 2 electrons from the new atoms will
move to the atom with 4
The Octet Rule is satisfied for all 3 atoms!
How do you figure out how many
You have an atom with
6 valence electrons…
And an atom with 1
valence electron
Will 1 of each atom bond?
No – they don’t meet the Octet Rule
How do you figure out how many
What is needed to
meet the Octet Rule?
I need 1 more atom
with 1 valence
electron
Then they have all 8 (or no)
valence electrons…
And all 3 will bond together
One more situation…
You have an atom with
8 valence electrons
It sees atoms with 1 and
2 valence electrons
Will the atoms bond?
No!
One more situation…
The first atom has 8
valence electrons
It already meets the
Octet Rule
The other 2 atoms don’t have enough to
either fully fill or empty their 8
So they won’t bond
One more situation…
What group of atoms
have 8 valence
electrons?
The Noble Gases
(group 18)
Because these atoms have all 8 valence
electrons…
They don’t bond (react) with other atoms
One more situation…
That is why the Noble Gases don’t react
They are monatomic atoms
The hermits of the Periodic Table
So now it is time for practice
You have a worksheet in front of you….
So now it is time for practice
Knowing what you know about the Octet Rule…
Fill in columns 2, 4, 5 and 6 of this table
So now it is time for practice
Knowing what you know about the Octet Rule…
For extra credit, fill in the information
in Column 7 (see example)
Your Homework…..
Finish your
Octet Rule
Worksheet