alkali metal(n = noun.substance)alkaline metal - any of the monovalent metals of group I of the periodic table (lithium or sodium or potassium or rubidium or cesium or francium); "the hydroxides of the alkali metals are strongly alkaline"
Any one of the univalent metals of group I of the periodic table of the elements, including lithium, sodium, potassium, rubidium, cesium, and francium. The hydroxides of these metals are soluble in water and form strongly basic solutions. [PJC.]