Balance the equation by putting the correct number in front of each compound. you can work this out mathematically or by drawing pictures on a piece of paper like the videos.

n2 + 02--> no2 forming nitrous oxide

N2 + 2O2 --> 2NO2

This is correct because you now have the same number of each element. Two Nitrogen, on the left side. So we made two on the right side. But after adding the second to the right side we then had 4 Oxygen on the right side. So we balanced the equation by adding an Oxygen to the left.  

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.