Question

Arrange the following as per the instruction given in the brackets:
He, Ar, Ne (Increasing order of the number of electron shells).

Answer 1

Hint: Electron shell can be thought of as an orbit in which electrons are revolving around the atom’s nucleus. Each shell has a fixed number of electrons. The number of shells increases with the period number, i.e. down the group.

Complete step by step solution
Helium: The symbol of helium is He. The atomic number of helium is two. Hence its electronic configuration is given by $ 1{s^2} $ . Helium is a colourless, odourless and tasteless gas. It is a non-toxic and inert monatomic gas. It is the first gas of the noble gas or the eighteenth group in the periodic table. Helium’s boiling point is the lowest in the periodic table. It is located in period 1.
Neon: The symbol of neon is Ne. The atomic number of neon is 10. Hence its electronic configuration is given by $ 1{s^2}2{s^2}2{p^6} $ . Under standard conditions, neon is a colourless and odourless gas. It is a monatomic gas. Neon is often used in sign boards. In vacuum tubes, high voltage indicators and television tubes, neon is used. The common method of extraction of neon is fractional distillation of liquid air. It is the second gas of the noble gas group or the eighteenth group in the periodic table. It is located in period 2.
Argon: The symbol of argon is Ar. The atomic number of argon is 18. Hence its electronic configuration is given by $ 1{s^2}2{s^2}2{p^6}3{s^2}3{p^6} $ . It is the third most abundant gas in the earth’s atmosphere. It is the third gas of the noble gas group or the eighteenth group in the periodic table. It is located in period 3.
When we go down the group in the periodic table, the electron shells are added to the elements. We can also say that, in successive periods, the electron shell number increases by one. Hence the order of elements according to the increase in number of electron shells is as follows, He < Ne < Ar.

Note
The first electron shell is K with a max of 2 electrons, the second shell is L with a max of 8 electrons, the third is M with a max of 18 electrons and the fourth shell is N with a max 32 electrons.