What are the 6 rules to deduce the oxidation number of any atom or ion by oxidaion?

1. Oxidation number of uncombined elements is zero 2. In compounds many atoms or ions have fixed oxidation numbers 3.The oxidation number of an element in a monatomic ion is always the same as the charge 4. The sum of the oxidation numbers in a compound is zero 5. Sum of oxidation number in an ion is equal to the charge on the ion 6. Either a compound or an ion, more electronegative elements is given negative oxidation number