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