(a) Lithium, sodium, and 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 unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?

(a) Since they only have one valence electron in their outermost shells, they are very unstable. Due to their easy reaction with water, hydrogen is released. They are also called alkali metals. In order to release hydrogen, they rapidly react with water.
(b)They are quite stable since their outermost shells are full. They only react under extreme conditions, therefore the name \”noble gases.\”