Question

The distribution of electrons In K, L, M, N shells of the following elements are given below:
$$\begin{array}{ccccc}\text{Elements}& \text{K}& \text{L}& \text{M}& \text{N}\\ \text{X}& 1& \text{-}& \text{-}& \text{-}\\ \text{Y}& 2& \text{8}& \text{2}& \text{-}\\ \text{Z}& 2& \text{8}& \text{8}& \text{-}\\ \text{W}& 2& \text{8}& \text{6}& \text{-}\end{array}$$
Which of the above element shows least chemical reactivity?

• A. X
• B. Y
• C. Z
• D. W

Answer 1

The correct option is C Z

From the Bohr-Bury scheme, we know that the outermost shell of an atom can accommodate a maximum of 8 electrons.
It is observed that the atoms of elements, completely filled with 8 electrons in the outermost shell show little chemical activity.
In other words, their combining capacity or valency is zero.
Therefore the correct option is Z.