All atoms of alkali metals have in common the same number of valence electrons. Alkali metals, which are found in Group 1 of the periodic table, each have one valence electron in their outermost electron shell. This characteristic is responsible for their similar chemical properties.
While alkali metals do not have the same number of protons (as that varies by element), neutrons (which can vary as well due to isotopes), or the same number of electron shells (which varies with the period in the periodic table), they all share the same number of valence electrons.
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