標題:
a question about oxidation
發問:
in a oxidation reaction. is it must have election lose?
最佳解答:
No. the definition of redox is "there's change in oxidation number of elements in a reaction". in LOK's example, gain / loss of electrons can lead to change of oxidation number. for example, Mg ------> Mg(2+) + 2e(-) the oxidation number of magnesium changes from 0 to +2 . however, in some reactions, there's no electron transfer, yet the oxidation number of elements changes. this's especially common in reactions involving covalent molecules. for example, C + O2 ------> CO2 in formation of covalent molecules, electrons are shared instead of transferred. oxidation number of C increases from 0 to +4, while O.N. of oxygen decreases from 0 to -2. you can see that electrons on carbon are NOT lost; it's shared with oxygen. Yet, O.N. of C increases and is oxidized. there're a lot more reactions of this type. for example, oxidation from ethanol to ethanoic acid, from sulphur to sulphur dioxide, from hydrogen to hydrogen chloride (a Covalent molecule!), etc.
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