Question

alkali metals do not form dipositive ions while alkaline metals form. why?

Answer 1

Alkali metals are members of Group I. They have only one electron in their outermost energy levels. To be stable they need to lose only that single electron in the outermost energy level thus forming monopositive ions.

Alkaline metals on the other hand have two electrons in their outermost energy level. They are members of Group II. To be stable, they lose these two electrons to form dipositive ions.