In the reaction n2(g) plus 3f2(g)---2nf3(g), the number of atoms of each element is conserved. This means that the number of nitrogen atoms and the number of fluorine atoms are the same on both sides of the equation.

To see this, let's count the number of atoms of each element on each side of the equation.

On the left side of the equation, we have:

1 nitrogen atom (n)

3 fluorine atoms (f)

On the right side of the equation, we have:

2 nitrogen atoms (n)

6 fluorine atoms (f)

As you can see, the number of nitrogen atoms and the number of fluorine atoms are the same on both sides of the equation. This means that the number of atoms of each element is conserved in this reaction.