Question

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

Answer 1

Lithium, Sodium , and potassium  are all metals having one free electron in them.  They become ions of 1 proton charge.  they have all valency of +1.  they all form  hydroxides and bases with water.  Chemical reactivity is high for these metals.

helium and neon have full number of electrons in their orbits in the atoms.  Both are called inert gases.  They have no affinity for becoming ions positive or negative.  they do not interact chemically with other elements.

Answer 2

Explanation:

(a) Lithium,  Sodium and Potassium all belong to the same group in the modern periodic table. When we take the electronic configuration of Lithium,  Sodium and Potassium there is only one electron in the outermost shell of these metals. They react vigorously with water to form alkalies.

Example: KOH, NaOH and LiOH

(b) Helium and Neon both are inert elements. Helium has its first shell completely filled with electrons its duplet is complete. The two shells of Helium which is completely filled is only K shell. Whereas for Neon its first and second shell are completely filled. Its octet is complete. The two shells of Neon which are filled are K and L shells.

Electronic Configuration:

Helium: 2

Neon: 2,8