The strong bases are hydroxides of group 1 and 2 metals (ex. Sodium, Potassium) or larger group transition metals (Copper, Iron), or oxides of the same metals.
It follows from structure of strong bases that they are composed of highly electropositive metals of groups 1 and 2 and the hydroxide ion.
Additionally, transition metals may also form bases with the hydroxide ion or oxides of this transition metals.
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