Feb23: Oxidation and Reduction

hello, last friday we learned about oxidation and reduction.
previously we learned that there are 5 type of reactions but on friday we learned that there are only two different families of chemical reactions:
1-those that don't have exchange of electrons-->non-redox reactions
2-those that do have exchange of electrons-->redox reactions

*when a substance lost/gave up its electrons it's an oxidation reaction:
Al(s) --> Al³⁺ + 3 electrons

*when a substance gains electrons it's called a reduction reaction:
Al³⁺ + 3 electrons --> Al(s)

to remember those key points we could use:
Oxidation
Is
Losing

Reduction
Is
Gaining
(OIL RIG)
or:
Losing
Electrons
Oxidation

Gaining
Electrons
Reduction
(Leo Ger)

also an important point is that Oxidation and reduction always occur at the same time, so that the number of electrons gained in a reaction is always equal to the electrons lost.
:. to keep track of the loss and gain of electrons in a reaction we use Oxidation States(imaginary charge an atom would have if both the electrons in an electron pain belonged to the most electronegative element of that pair)
Oxidation numbers are positive and negative numbers that are related to an atom's oxidation state.

the most important part of the lesson was knowing the 9 rules applying to the concept.
DUH RULES:
1-The oxidation number of an atom in an uncombined element is zero.
ex. O₂

2-the SUM of the oxidation numbers of the elements in any neutral molecule is zero.
ex. MgCl₂
+2 + (-1 x 2)= 0

3-the sum of the oxidation numbers of the elements in any ion is equal to the charge on the ion.
ex. NO₃^-1
+5 + (-2 x 3) = -1

4-in compounds the oxidation number of many elements corresponds to their position on the periodic table.
a)elements in Group 1A are always {+1}
ex. H , Li, Na, K, Rb, Cs, Fr

b)the alkaline earth metals are always {+2}
ex. Be , Mg, Ca, Sr, Br, Ra

c)aluminum is always {+3} and zinc is always {+2}

d)halogens are almost always {-1}
ex. F , Cl, Br, I, At

e)Hydrogen always has an oxidation number of {+1} when it's combined with non metals.
ex. HCl

f)oxygen has an oxidation number of {-2} in most compounds (exception:in peroxides where it is -1, ex. H₂O₂ (hydrogen peroxide)
ex. SO₂ S is +4 and O is -2

i guess that's all!
i think we have a scribe for today, so i won't pick.