Well, a mole of ##"nitrogen atoms"## has HALF the mass of a mole of ##"nitrogen molecules"##

Well, a mole of ##"nitrogen atoms"## has HALF the mass of a mole of ##"nitrogen molecules"##.

The dinitrogen molecule, ##N-=N##, contains TWO nitrogen atoms; and of course has twice the number of atoms, and twice the mass of an isolated nitrogen atom, ##N##.

Inorganic chemists often speak of the ##"dinitrogen"## or ##"dihydrogen"## or even the ##"dioxygen molecule"## to distinguish the molecular species from the individual atoms: i.e. ##N_2##, ##H_2##, ##O_2##, versus atomic, ##N##, ##H##, ##O##.

This concept of molecularity is crucial to understanding and problem solving in inorganic chemistry. Most elemental gases (save for the Noble Gases) are BIMOLECULAR, and you will be expected to know this.