oxidation number既問題..............

弄清楚concept先...

oxidation 係指放電子既反應
而reduction 係指收電子既反應

而oxidation number係指電子放出既數目。

希望可以幫到你，唔好因為見到有「氧」/ oxi 搞亂

2008-05-22 21:51:48 補充：
Fixed Oxidation munber:

Uncombiled element (eg O2, F2, Cl2): 0
metal atom: 0
O: -2 (exception: H2O2, Na2O2, K2O2 -1)

F: -1

Halide (Cl, Br, I) : -1 (exception:: NaOCl= +1, NaClOs= +5)

All group II element: +2

All group I element: +1

Hydrogen: Mostly +1 (exception: reaction between group I metals)

oxidation number 係唔關 oxygen 事
佢係一隻 element 響 compound 入面帶既 charge
好似 NO2 咁
O 有一個 fixed ON = -2
而 NO2 overall charge = 0
所以
ON of N + ON of O x2 = 0
ON of N + (-2)x2 = 0
ON of N in NO2 = +4
又好似 MnO4- 咁
O 有一個 fixed ON = -2
而 MnO4- overall charge = -1
所以
ON of Mn + ON of O x4 = -1
ON of Mn + (-2)x4 = -1
ON of Mn in MnO4- = +5

Firstly, you should clarify your concept.
Oxi-dation number is no direct relationship between Oxygen and O.N..

Oxidation = Increase in O.N. = LOSE Electron = Reducing Agent
Reduction = Decrease in O.N. = Gain Electron = Oxidizing Agent
The Oxidation number of an element in a compound is the charge an atom of the element would have if the atom existed as an ion.
There are several rules for assigning oxidation number, but I am not going to tell you one by one, just give you some of them.

- ON of Free element = 0
e.g. O2, Cl2, N2 - Containing only one kind of atoms
- ON of Simple ion = CHARGE
e.g. ON of SO42- = -2
ON of OH- = -1
ON of H+ = +1
- ON of all elements in a compound =0
e.g. HCL, H2O, H2SO4