Rules for the negatively charged ions. The negative charge shows how many electrons atom gains to reach the noble gas configuration. Oxidation number rules for Elements and Monoatomic Ions. The oxidation number of any element is zero. The oxidation number of any monoatomic ion is the same as the charge on this ion.
All redox reactions involve electron transfer.
Oxidation removal of electrons. Reduction gain of electrons. Reducing agents cause reduction. Oxidizing agents cause oxidation. Example of a redox reaction and assignment of oxidation numbers.