oxidation number

Oxidation number (下稱ON)通常同
(1)個ion既charge
(2)個ion在compound既charge
一樣。
最多ON change既atom係H同O。

就咁Oxygen(O2) 既ON，係0。
你指既應該係oxide ion
普通 oxide ion，即係O2- 係-2
如MgO, K2O,...等

係Hydrogen peroxide(H2O2), 呢度既H既ON係+1, 因為H2O2既charge 係0, 佢既ON都係0.
2 x ON of H + 2 x ON of O = 0(因為有2個H同2個O)
2 x 1 + 2 x ON of O = 0
ON of O = -1
係H2O2 入面，O既ON係-1
其實佢係O22- ，不過CE入面都會當一個O既ON係-1
同一個case入面，hydrogen既ON係+1

hydrogen既ion有2種，一個就係hydrogen ion (H+), 一個係hydride ion (H-)，可見hydrogen 既ion 既ON有+1同-1
-1既example: NaH

a compound is formed from two or more elements.
in a compound, whether an element gets a negative oxidation number
is determined by the electronegativity of the element.
for example, sodium oxide, oxygen is more electronegative
than sodium, so it is assigned negative ON. it is -2
in hydrogen peroxide, it is -1
but in OF2 , a covalent compound formed from oxygen and
flourine , oxygen is +2, because flourine is more
electronegative than oxygen.
in the case of hydrogen, it is usually+ 1, such as
HCL.
but for sodium hydride, since hydrogen is more electronegative
than sodium, it is assigned -1.