7.1.1 Oxidation numbers Redox reactions are considered as electron-transfer reactions. Cu2(aq)+Zn(s)-Zn(aq)+Cu(s) Electrons acceptance&donation电子得失 H2(g)+Cl2 g)=2HCI (g) Electron excursion电子偏移 Oxidation number:the number of charges the atom would have in a molecular(or an ionic)compound if electrons were assumed to be transferred completely. 7.1.1 Oxidation numbers Oxidation number ：the number of charges the atom would have in a molecular(or an ionic) compound if electrons were assumed to be transferred completely. Redox reactions are considered as electron-transfer reactions 。 Cu (aq ) Zn ( s ) Zn (aq ) Cu ( s ) 2 2 + + + + Electron excursion 电子偏移 H 2 ( g ） +Cl 2 （g ） 2HCl （g ） Electrons acceptance & donation 电子得失