1. CHEMISTRY BASICS Inside the atom…. There is the nucleus
The nucleus has protons and neutrons
The protons have a positive electrical charge
And the neutrons don’t have any electrical charge

2. So overall, the nucleus….
Has a positive electrical charge
The electrons have a negative electrical charge
So this holds the electrons in their orbitals

3. There are several layers of orbitals…
And there are electrons in each layer
So overall,
The positive charge in the nucleus balances the negative charge of the electrons
So the atom has a neutral charge

4. But when 2 atoms get close…
Something else happens…..
The negative electrons of one atom…
Feel the positive nucleus of the other atom
And the electrostatic forces hold them together

5. It isn’t always a happy meeting….
The electrons on one atom like the nucleus of another atom
But the electrons on that atom don’t like the electrons
And they don’t want the other electrons near

6. So when they do get close…..
The electrons have to move around each other
How they move around each other controls what kind of chemical bond is made

7. Not all of the electrons care…
Remember the different orbital layers….
The electrons on the outside may see the other atom…
But the electrons close in are happy with their own nucleus

8. Not all of the electrons care…
So only the outer or valence electrons…
Interact with the other atoms to make a chemical bond

9. Valence Electrons
When an atom undergoes a chemical reaction, only the outermost electrons are involved.
These electrons are of the highest energy and are furthest away from the nucleus. These are the valence electrons.
The valence electrons are the outermost s and p electrons.

10. Predicting Valence Electrons
The Roman numeral in the American convention indicates the number of valence electrons.
Group IA elements have 1 valence electron
Group VA elements have 5 valence electrons
When using the IUPAC designations for group numbers, the last digit indicates the number of valence electrons.
Group 14 elements have 4 valence electrons
Group 2 elements have 2 valence electrons

11. Not all atoms can bond It depends on the number of valence electrons
Think of…..
…..An apartment building
8 apartments / floor
“Eight is Great”

12. When atoms bond…
If they can’t fill or empty a floor
The atoms don’t want to bond

13. 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 fully empty or full

14. This atom takes its electrons
And moves them to the other atom
Now both atoms are happy and can bond

15. Here’s how it works…. This is called the “rule of eight”
Or the “Octet Rule”
Remember – “Eight is Great”

16. If the atom can’t fill or empty the floor…
The Octet Rule isn’t followed…
And the atoms don’t want to bond

17. Here’s an example An atom with 3 valence electrons
Comes near an atom with 5 valence electrons
Will these atoms bond?

18. Here’s an example Yes! This atom moves its 3 electrons
Into the 3 empty places in this atom
And the atoms will get together and bond

19. Another example: An atom with 2 valence electrons
Sees an atom with 5 valence electrons
Will these atoms bond?

20. How could they bond? But this atom still needs one for the Octet Rule
Move the electrons and this atom is happy…
Where could they get it?
A 3rd Atom with one electron

21. 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!

22. 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

23. 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!

24. 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!

25. 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

26. 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

27. That is why the Noble Gases don’t react
They are monatomic atoms
The hermits of the Periodic Table