Nitrogen cycle INDEX

Nc, Nh, Nx, Nn, Np, and C are the number of carbon atoms, hydrogen, halogen, nitrogen, phosphorous, and independent cycles, respectively. Nq-s and Nsos are the number of oxygen atoms bonded to sulfur and the number of SO3 groups, respectively. When no sulfur atoms are present, this index can be easily calculated from the chemical formula otherwise, it is coincident with the index calculated replacing b with b, the multiple bond count. 

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