Understanding Oxidation Numbers
* Oxidation numbers are a way of keeping track of the electrons in a molecule or ion. They represent the hypothetical charge an atom would have if all the bonds were ionic.
* Rules for assigning oxidation numbers:
* The oxidation number of an element in its elemental form is 0.
* The oxidation number of a monatomic ion is equal to its charge.
* The oxidation number of oxygen in most compounds is -2 (except in peroxides, where it's -1).
* The oxidation number of hydrogen in most compounds is +1 (except in metal hydrides, where it's -1).
* The sum of the oxidation numbers in a neutral molecule is 0.
* The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion.
Applying the rules to hydrazine (N₂H₄):
1. Hydrogen's oxidation number: In hydrazine, hydrogen is bonded to nitrogen, so its oxidation number is +1.
2. Let x be the oxidation number of nitrogen: Since there are two nitrogen atoms in hydrazine, the total oxidation number for nitrogen is 2x.
3. Sum of oxidation numbers: The sum of the oxidation numbers in hydrazine must equal zero: 2x + 4(+1) = 0
4. Solve for x: 2x + 4 = 0 => 2x = -4 => x = -2
Therefore, the oxidation number of nitrogen in hydrazine is -2.
