Question

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

We need to study about two elements namely helium and neon. These two gases belong to group 18 of the periodic table. This group consists of helium, neon, argon, krypton, xenon, and radon with helium at the top of the group 18 and radon at the bottom.These elements are usually gases and are also called noble gases. We will discuss the reactivity of these elements and find out if helium and neon have in common.

Complete step by step answer:
We need to analyse the reactivities of helium and neon and find what they have in common. As we know, helium and neon belong to the noble gas elements. Noble gases are elements of the group 18 which are also called inert. Inert gases are those which are so stable that they do not react or have very less tendency to react. The reason for this is that they have a stable electronic configuration. As the name suggests, noble gases mean the gases which do not react with anything hence also known as inert gases. These gases have 2, 8, 8 electrons in their outer shell with a complete octet hence very stable and very inert.
Hence, we cay that helium and neon have the following in common:
They belong to same group of the periodic table
Their last shell is filled hence they do not require more electrons unlike other elements which react with other elements to complete their octet.

Note: We must be noted that another reason why helium is totally unreactive is because of its small atomic size. Atomic size increases as we go down the group. Hence neon is of low reactivity due to a bigger atomic size than helium. This does not mean that radon being at the bottom of the inert gas group will be extremely reactive. In fact the reactivity of radon is also negligible.