11. The oxidation number of the most common chalcogen compounds with positive metals is " 2. 12. Other oxidation numbers , such as " 1 in pyrite and peroxide, do occur. 13. For oxygen ( O ) the oxidation number began as 0 and decreased to 2 ". 14. Having said all that, it is unusual to have to indicate a negative oxidation number . 15. When the metal has more than one possible ionic charge or oxidation number the name becomes ambiguous. 16. Because of this, the oxidation number of Pt does not rise above + 2.32. 17. It is possible to determine the strength of the nuclear charge by the oxidation number of the atom. 18. When methane is oxidized to carbon dioxide its oxidation number changes from " 4 to + 4. 19. But you need to actually know how to assign oxidation numbers before you can do anything else here. 20. The sum of the oxidation number of all atoms in a compound is zero . " "'
