Question

What are the similarities in the electronic structure of the following sets of atoms?
(a) Helium, neon and argon
(b) Beryllium, magnesium and calcium​

Answer 1

a) They both have their outer electron shell filled, so they have no tendency to acquire or lose an electron.

(He 2, Ne 2-8, Ar 2-8-8)

Therefore, they are very unreactive, a reason they are also called inert gases.

b) Beryllium, magnesium and calcium all have 2 electrons in outermost shell.