It's a chemistry question.

1 mol of Nitrogen atom has a mass of 14 g.

The relative mass of nitrogen is 14, if you look at your periodic table. One mole of any atomic substance has the same mass as their relative mass and you only need to and the units, that is the grams.

Now, if you're dealing with molecules, one mole of nitrogen gas () contains twice the amount of Nitrogen atoms, hence the mass is twice.

Use proportions to find the mass of any other amount of moles.