Any element of the group of alkali metals in the periodic table.
any of the monovalent metals of group I of the periodic table (lithium or sodium or potassium or rubidium or cesium or francium)
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"
