Question

The oxidation number of an element in a compound is evaluated on the basis of certain rules , Which of the following rules is not correct in this respect?

• A. The oxidation number of hydrogen is always +1.
• B. The algebraic sum of all the oxidation numbers in a compound is zero.
• C. An element in the free or the uncombined state bears oxidation number zero.
• D. In all its compounds , the oxidation number of fluorine is -1.

Answer 1

The correct option is A The oxidation number of hydrogen is always +1.

A. The oxidation number of hydrogen can be +1 or -1 or 0 . For example , in metal halides as NaH it is -1, in hydrogen halide as HCl it is +1 and in dihydrogen $H_2$ it is 0.

B. The algebraic sum of all the oxidation numbers in a compound is zero.

example: $H_{2}O$ it is $2\times 1-2=0$

C. An element in the free or the uncombined state bears oxidation number zero.

D. In all of its compounds ,the oxidation number of fluorine is -1 because it is being most electronegative element in the periodic table,