Ncert Exercises & Solutions

Which of the following statement regarding the rules to calculate the oxidation number is incorrect?

1.	The oxidation number of hydrogen is always +1.
2.	The algebraic sum of all the oxidation numbers carried by elements in a compound is zero.
3.	An element in its free or uncombined state has an oxidation number of zero.
4.	Generally, in all its compounds, the oxidation number of fluorine is -1.