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….

Working with table…

Count from left…

3 4 5 6 7 81 2

Or look at column number

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…..

This building has 8 apartments / floor

…..An apartment building

“Eight is Great”

Not all atoms can bond Each floor of the apartment is an element or atom

The Number of full or empty “apartments”….

…is important to the “landlord” atom

Valence electrons live in

the apartments….

Not all atoms can bond When atoms bond…

Atoms work together to move electrons

So that each atom has either…

…an empty or full floor

from “apartment” to “apartment”

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 exampleAn atom with 3 valence electrons

Comes near an atom with 5 valence electrons

Will these atoms bond?

Here’s an exampleThis atom moves its 3 electrons

Into the 3 empty places in this atom

And the atoms will get together and bond

Yes!

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 atomsYou 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 manyYou 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 manyWhat 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 practiceKnowing what you know about the Octet Rule…

Fill in columns 2, 4, 5 and 6 of this table

So now it is time for practiceKnowing 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