* Astronomy

The alkali metals are a series of chemical elements comprising Group 1 (IUPAC style) of the periodic table: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). (Hydrogen, although nominally also a member of Group 1, very rarely exhibits behaviour 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 characterised homologous behaviour down the group.

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