<P> The alkali metals are all shiny , soft , highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge + 1 . They can all be cut easily with a knife due to their softness , exposing a shiny surface that tarnishes rapidly in air due to oxidation by atmospheric moisture and oxygen ( and in the case of lithium , nitrogen ) . Because of their high reactivity , they must be stored under oil to prevent reaction with air , and are found naturally only in salts and never as the free elements . Caesium , the fifth alkali metal , is the most reactive of all the metals . In the modern IUPAC nomenclature , the alkali metals comprise the group 1 elements , excluding hydrogen ( H ) , which is nominally a group 1 element but not normally considered to be an alkali metal as it rarely exhibits behaviour comparable to that of the alkali metals . All the alkali metals react with water , with the heavier alkali metals reacting more vigorously than the lighter ones . </P>
<P> The alkali metals are all shiny , soft , highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge + 1 . They can all be cut easily with a knife due to their softness , exposing a shiny surface that tarnishes rapidly in air due to oxidation by atmospheric moisture and oxygen ( and in the case of lithium , nitrogen ) . Because of their high reactivity , they must be stored under oil to prevent reaction with air , and are found naturally only in salts and never as the free elements . Caesium , the fifth alkali metal , is the most reactive of all the metals . In the modern IUPAC nomenclature , the alkali metals comprise the group 1 elements , excluding hydrogen ( H ) , which is nominally a group 1 element but not normally considered to be an alkali metal as it rarely exhibits behaviour comparable to that of the alkali metals . All the alkali metals react with water , with the heavier alkali metals reacting more vigorously than the lighter ones . </P>
which element in group 1 is not an alkaline metal
which element in group 1 is not an alkaline metal
hydrogen
hydrogen