The #"Periodic Table"# divides the 100 of so known elements into vertical columns, so-called #"Groups"#, and so-called #"Periods"#, horizontal rows. The #"Groups"# and #"Periods"# fill on the basis of repetitive electronic structure. Members of the same #"Group"# display reasonably similar chemistry.
Members of #"Group 1"# are the so-called #"alkali metals: lithium; sodium; potassium; rubidium........"#