Where are the most vicious alkali metals?
What are the most reactive alkali metals?
The reactivity of the alkalis INCREASES down the Group.
Lithium, and sodium, can be handled ROUTINELY. Potassium, and caesium demand a little more respect. You probably will not even find potassium in most modern laboratories (unless it is an old bottle, where the metal is stored under oil in order to protect it from atmospheric moisture.)