The chemical potential of electrons is slightly different from the chemical potential of a compound or a substance.
Please read here:
https://en.wikipedia.org/wiki/Chemical_potentialhttps://wiki.fysik.dtu.dk/ase/ase/thermochemistry/thermochemistry.htmlC.J. Cramer. Essentials of Computational Chemistry, Second Edition. Wiley, 2004.
For the chemical potential of N2 gas, you can calculate it according to the ideal gas approximation once you do the vibration frequencies.
Alternatively, you may calculate the chemical potential of N2 gas by use of the data listed in
Chase, M. W. J. NIST-JANAF Themochemical Tables, 4th ed.; AmericanInstituteofPhysicsandTheAmericanChemicalSociety:
Washington DC, 1998;
Cox, J. D.; Wagman, D. D.; Medvedev, V. A. CODATA Key
Values for Thermodynamics; Hemisphere Publishing Corp.: New York,
1989;