Every metals of group I of the periodic table like lithium or sodium or potassium or rubidium or cesium or francium. NaK, or sodium-potassium alloy, is also considered an alkali metal because it is a mixture of two alkali metals, sodium and potassium. Almost all the alkali metals are very reactive with air and water. The water reaction is strong to the explosive and produces hydrogen gas and hydroxides. The hydroxides of these alkali metals are very strongly alkaline. Alkali metals are available in some Gulf of Mexico sediments--Amended rubidium values and K/Rb ratios.Properties
The alkali metals reveal many of the physical properties which is common to metals, although their densities are lower than those of other metals. Alkali metals have one electron in their outer shell, which is loosely bound which in turn gives them the largest atomic radii of the elements in their respective periods. Their low ionization energies end result in their metallic properties and high reactivity. An alkali metal can be easily losing its valence electron to form the univalent cation. Alkali metals have low electro negativities which react readily with the nonmetals, particularly halogens.