Re: Why is lithium less reactive than potassium

A Table of Standard Reduction Potentials (college general chemistry text,
freshman level)gives the potential for Li of
-2.9595V (Li <--> Li(+) + e-) and K -2.9241V.  Using this criteria (larger
reduction potential), Li is MORE reactive than K and the premise of the
question is wrong.  Offhand I don't know of any circumstances where K is
more reactive than Li.  Fluorine is more reactive than iodine.

The reason for this is that the ions of Li (Li+ ion) & F (F- ion) assume the
electronic (outer shell) structures of the Noble Gasses (He in the case of
Li+, Ne in the case of F-).  These outer shell electron configurations are
especially stable and make (F-) and (Li+) more stable than F and Li.  In
order to understand why these particular electronic configurations are
stable the questioner should find introductory books on the Electronic
Structure of Atoms in a college library.  The chapters on this topic in a
freshman level General Chemistry text may also be helpful.