alkali metal

The alkali metals are a series of elements comprising Group 1 (IUPAC style) of the periodic table: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). (Note that hydrogen, although nominally also a member of Group 1, very rarely exhibits behavior comparable to the alkali metals). The alkali metals provide one of the best examples of group trends in properties in the periodic table, with well characterized homologous behavior down the group.
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Noun
1. 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"
(synonym) alkaline metal
(hypernym) metallic element, metal

n. alkali

family of group IA metals in the periodic table made up of, lithium, Li, sodium, Na, potassium, K, rubidium, Rb, cesium, Cs, and francium, Fr, all group IA elements except hydrogen, H. The oxides and hydroxides of these metals are strong bases. See also, alkali.

 Say it 
(alkaline earth metal) The Group 1 elements, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr) react with cold water for form strongly alkaline hydroxide solutions, and are referred to as "alkali metals". Hydrogen is not considered an alkali metal, despite its position on some periodic tables.