ok,I really don't understand the whole oxidation numbers thing my question is state the oxidation number for nitrogen in the following

NH3= -3
NO2-1= -1
N2= 0
NO2Cl= 5
N2H4 -2
am I correct?

NH3= -3
NO2-1= -1 No, oxygen is -2, so N is +3
N2= 0
NO2Cl= 5
N2H4 -2

http://www.chemistry.co.nz/redox_oxi_aa.htm

The oxidation number (also known as oxidation state) of an element in a compound represents the hypothetical charge that element would have if all bonds in the compound were purely ionic. To determine the oxidation number of an element in a compound, you generally have to follow a set of rules.

In the case of nitrogen (N) in the given compounds:

NH3: The sum of oxidation numbers for atoms in a neutral compound is always zero. Since hydrogen (H) has a fixed oxidation number of +1, we can calculate the oxidation number for nitrogen (N) as follows:

(3 * (+1)) + (1 * (X)) = 0
X = -3

So the oxidation number of nitrogen in NH3 is -3.

NO2-1: Oxygen is generally assigned an oxidation number of -2, but in this case, we have two oxygen atoms and the overall charge of -1. By substituting these values into the equation, we can calculate the oxidation number for nitrogen (N):

(2 * (-2)) + (1 * (X)) = -1
X = +3

So the oxidation number of nitrogen in NO2-1 is +3, not -1 as you initially suggested.

N2: In a molecule consisting of two atoms of the same element (like N2), the oxidation number is always zero. So the oxidation number of nitrogen in N2 is 0.

NO2Cl: Here, nitrogen (N) is bonded to two oxygen atoms and one chlorine atom. Since oxygen is -2 and chlorine is -1, we can calculate the oxidation number for nitrogen (N):

(2 * (-2)) + (1 * (X)) + (1 * (-1)) = 0
X = +5

So the oxidation number of nitrogen in NO2Cl is +5.

N2H4: Again, in a molecule consisting of two atoms of the same element (like N2), the oxidation number is always zero. So the oxidation number of nitrogen in N2H4 is 0, not -2 as you initially suggested.

To verify these results and for further explanations, you can refer to the link you provided: http://www.chemistry.co.nz/redox_oxi_aa.htm