Place the species below in order of shortest to longest nitrogen-nitrogen bond.

\[\mathrm{N}_{2}, \mathrm{~N}_{2} \mathrm{~F}_{4}, \mathrm{~N}_{2} \mathrm{~F}_{2}\]

( \(\mathrm{N}_{2} \mathrm{~F}_{4}\) exists as \(\mathrm{F}_{2} \mathrm{~N}-\mathrm{NF}_{2}\), and \(\mathrm{N}_{2} \mathrm{~F}_{2}\) exists as \(\mathrm{FN}-\mathrm{NF}\).)