Definition of alkali metal

1) A metal in the first column of the periodic table (i.e., lithium, sodium, potassium, rubidium, cesium and francium). With the exception of francium, these metals are all soft and silvery. They may be readily fused and volatilized with their melting and boiling points becoming lower with increasing atomic mass. They are the strongest electropositive metals. These elements react vigorously, even violently with water.