why is NO equal to nitrogen oxide

isn't the charge of N ion +3?

Nitrogen is a multivalent compound,in this case, it is +2.

what does multivalent mean

http://www.memidex.com/multivalent+chemistry

Nitrogen has COMMON oxidation states of -3, 0, +1, +2, +3, +4, +5

examples:
-3 in NH3
0 in N2
+1 in N2O (laughing gas)
+2 in NO
+3 in N2O3
+4 in NO2
+5 in N2O5 and HNO3

NO refers to nitrogen monoxide, which is a molecule consisting of one nitrogen atom (N) and one oxygen atom (O). It is also known as nitric oxide. On the other hand, nitrogen oxide is a term used to describe any compound consisting of nitrogen and oxygen.

Regarding the charge of the N ion, nitrogen typically forms three bonds. However, nitrogen oxide (NO) is a neutral molecule and does not have an overall charge. The nitrogen atom in NO shares one electron with the oxygen atom, forming a covalent bond. Therefore, the nitrogen atom in NO does not have a formal charge of +3.

To conclude, NO is nitrogen monoxide, which is a neutral molecule consisting of one nitrogen atom and one oxygen atom. It is different from nitrogen oxide, a broader term describing any compound composed of nitrogen and oxygen.