Q.4. (b) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?
Both Helium and Neon are noble gases which belong to the zero groups in the modern periodic table. They have fully filled the outermost shell with electrons.
Helium has two electrons in its K shell whereas Neon has 8 electrons in its outermost shell.