[AussieKenDoll]

Out of the two N atoms on the nicotine, which one is more basic? and why?

[hollytara]

The N-methyl pyrrolidine is more basic (pKb ~6) while the pyridine is less basic (pKb ~10).  If you look up crystal structures of nicotinium salts, they are protonated on the pyrrolidine.  This is less basic than expected for a tertiary amine (pKb usually 3-4) and for a pyridine (usually ~9). The difference is less in the gas phase - the two basic sites are sufficiently similar in energy that protons will be exchanged between the two.