Alkali metals possess a valence of 'negative one,' whereas the halogens possess outer electron shells within which reside singular electrons. They also differ in state at those temperatures at which humans are generally most comfortable (the low- to mid-20s in degrees Celsius).
When given reason to react with other metallic elements, those substances in the first group of the periodic table will produce 'metallic compounds,' in which the atoms of these differing metals are bound to one another in such a manner that electrons may move freely throughout the material overall, and travel towards positive charges within the matter of their 'parent substances' overall, where such exist. Halogens which form bonds with metallic substances produce ionic compounds, which often generate a salt precipitate. These ionic compounds are formed through the means of electrons from 'incomplete' outer shells entering into the orbit of other atoms, to enter a more attractive external orbit (ex: one with greater positive charge than the preexisting)
Simply put, the alkalis are metallic substances with seven electrons in their outermost shells. At the temperature of an average indoor area, all alkali metals should be found in solid form. The halogens are materials that may occur in solid, liquid, or gaseous state at room temperature; the final shell surrounding any atom of this sort of substance will always contain only one electron.
Hope it helps u..!!!
