2. Representatives
• We have talked about the Representative
elements…
• Groups 1A through 8A
• And ion formation
IonIon
chargecharge
GroupGroup
numbernumber
valencevalence
numbernumber # of e-# of e-
lost orlost or
gainedgained
3. Transition elements
• Found in the middle of the table
• Known as the B group elements
• Are called transition because they can change
their charges!
• How do they become charged?
• By losing electrons.
5. How do we predict???
• Cannot use group number!
• Must see how it reacts with other
elements.
• Need to see its OxidationOxidation
state (+ or -).state (+ or -).
6. Oxidation state
• Represents the charge of an atom in a
compound at a given time.
– It is similar to the charge on the atom.
• To figure, need to know the oxidation
state rules…
7. OXIDATION RULES
1. Oxidation state of an element (in its pure form)
is 0.
2. Oxidation state for representatives is their
ionic charge most of the time.
3. Oxygen is always –2 unless in a peroxide,
then it is –1.
4. H with nonmetals(covalent compounds) is
given +1 oxidation state. Usually in the front
of the formula.
5. The sum of oxidation numbers must be 0 for
compounds and whatever the charge of the
ionic species is.
8. To use rules:
• You need to be able to do two
things:
An atom inventory
Add and multiply whole numbers that are
positive and negative.
9. Examples:
Find oxidation states for all elements present.
• CO2
C
O
1
2
x
x
=
=
0
-2 -4
+4+4
Total charge
of compound
#ofatoms
times
Oxidationstate
Totalchargeperelement
Elementsymbol
equals
