question_answer 11)

                (a) Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements? (b) Helium is an un reactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?                                           

Answer:

(a) Lithium, sodium and potassium all react with water to form alkalis, i.e., lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. with the liberation of hydrogen gas.   All these metals have one electron in their respective outermost shells.        (b) Helium and neon are noble gases and hence have extremely low chemical reactivity. The common thing in these gases is that they have their shells completely filled. Helium has only K-shell which is complete, i.e., has 2 electrons. Neon, on the other hand, have two shells, K and L. Both these shells are complete, i.e., K shell has 2 electrons and L shell has 8 electrons.