Question
Why are some elements in molecular form while others are in atomic form?
Solution
Elements of stable configuration exist in atomic form. For example, inert gases— He, Ne, Ar and other noble gases. They have fully filled electronic configuration. Hence the atomic form is stable.
Elements which are short of inert configurations by 1, 2 or 3 electrons (outermost shell contains 5, 6, 7 electrons) achieve stable configuration by sharing requisite number of electrons with other atoms and exist in molecular form. For example, chlorine atoms have 7 electrons in their outermost shell, thus two Cl atoms share one electron of each other and exist as Cl—Cl (Cl2).
Elements which are short of inert configurations by 1, 2 or 3 electrons (outermost shell contains 5, 6, 7 electrons) achieve stable configuration by sharing requisite number of electrons with other atoms and exist in molecular form. For example, chlorine atoms have 7 electrons in their outermost shell, thus two Cl atoms share one electron of each other and exist as Cl—Cl (Cl2).
