How does the reactivity of metals change from top to bottom on the periodic table?
...the valence electrons are PROGRESSIVELY FARTHER REMOVED from the nucleus...and thus the lower metals should be BETTER REDUCING AGENTS.
And this is certainly observed in the alkali metal series. Both lithium and sodium are quite active metals, however, potassium (and its alloys) are pretty hairy metals to handle, and WILL ignite ethyl alcohol should you attempt to quench the metal with this solvent. A different solvent mix must used to destroy residues of these metals.