Oxidation Number

Why do Ions form?

• In order to understand why ions form, you need to know how Electrons are arranged!

• Where are electrons located???

Quick Review of Electron Configuration

• Electrons are found in the electron cloud, but they’re not just placed anywhere.

• Electrons are found on different energy levels around the nucleus, and each energy level has a maximum number of electrons that it can hold

• 1st level = 2 2nd level = 8• 3rd level = 18 4th level = 32• Keep in mind, these are the maximum they can hold and

not always the most stable configuration.

How do they get in there?

• Electrons start at the lowest level and work their way up, so always start in the first level.

• How many does the first level hold?• They fill in a the first level before going on to

the next.• NOTE: if it is the outermost energy level, 8 is

maximum number of electrons

• Take the element Boron!

• How many Protons?

• How many Neutrons?

• How many Electrons?

• Where will they go?

5

6

• Take the element Neon!

• How many Protons?

• How many Neutrons?

• How many Electrons?

• Where will they go?

10

10

Put on your thinking caps

• What do you remember about the Noble gases?

• Stable because of its unique electron formation, stable outer energy level!

• Octet Rule – Every atom wants to be in a stable form, this occurs when an atom has a stable outer energy level. (Usually 8 valence electrons in it outer energy level – A few exceptions….)

Unlocking the secrets of bonding, one electron at a time

• So, Atoms want to always be stable, but how can we determine what they will do?

• It’s all based on their number of valence electrons (electrons in outermost energy level).

• Lets go back to Boron!

• Look at Boron in it’s normal state

• Not stable! – NO OCTET! so what is easier and quicker for this atom?

• Gain 5 more or loose 3?

• And the winner is…..

STABLE 1st ENERGY LEVEL

Oxidation Number

• Congrats! You just determined the oxidation number for Boron!

• Oxidation number is the number of electrons an atom gains or loseswhen bonding.

Ox-a-what?!

All the steps you need • 1) Find the element and figure out how many

electrons it normally would have. (Remember it’s the same as Protons)

• 2) Ask yourself, how many valence electrons does this atom have? (Those are the ones on the outer energy level)

• 3) Would it be quicker to add and get 8 valence electrons, or lose them and go down to a stable lower level? (I don’t think you need a hint here, it’s literally that easy)

Practice

A) Nitrogen B) Fluorine

C) Phosphorus D) Chlorine

What did you notice?

• What did you see about atoms that are in the same groups?

• Remember that these elements in the same columns have similar electron configurations!!!!

• SO…..Every atom in the same group has the same electron configuration! Ready for a big helping hint??? Get out your Periodic Table and check this out!