Question

(a) What are noble gases?

(b) What is the specialty of their outermost shells?

(c) In which group they are placed?

(d) Why is that Group referred to as Zero group?

(e) Why are they referred to as inert gases?

Answer 1

(a)

• Modern periodic table is the arrangement of elements on the basis of increasing atomic number in 7 horizontal rows and 18 vertical columns. Horizontal rows are termed as periods while the vertical columns are termed as groups.
• Elements present in Group 18 of the periodic table are termed as noble gases. It includes Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Ra).

(b)

• Valence electrons of any element is defined as the number of electrons present in the outermost shell of any element.
• In case of Group 13 to 18, the formula to calculate the number of valence electrons is:

$\mathrm{Number}\mathrm{of}\mathrm{valence}\mathrm{electrons}=\mathrm{Group}\mathrm{number}-10$

• Substitute 18 for Group number to calculate the number of valence electrons in noble gases or inert gases.
• $\begin{array}{rcl}\mathrm{Number}\mathrm{of}\mathrm{valence}\mathrm{electrons}& =& 18-10\\ & =& 8\end{array}$
• Since all the elements of Group 18 have 8 valence electrons except Helium (He), all the elements of Group 18 have a completely filled outermost shell.

(c)

• Noble gases or inert gases elements are present in Group 18 or zero Group of the periodic table.

(d)

• Since the maximum number of electrons that are filled in the outermost shell is 8 in spite of the fact that it can accommodate more than 8 electrons, all the elements of Group 18 have a completely filled outermost shell.
• Due to the presence of maximum electrons in their outermost shell, these elements have zero tendency to accept or lose any electron.

(e)

• The ability of any atom to lose or gain electrons in order to participate in any chemical reaction is termed as reactivity.
• Since noble gases do not lose or gain electrons, they are chemically inert and are classified as inert gases.