Question

Arrange the given elements in the increasing order of their valency:

• A. Lithium
• B. Beryllium
• C. Boron
• D. Carbon

Answer 1

Valency is the combining capacity of an element.
The number of electrons present in the outermost shell are called the valence electrons and they determine the valency of the element.

A short-cut method is used to calculate valency :
If no. of valence electrons are less than or equal to 4:
valency = valence electrons
If no. of valence electrons are more than 4:
valency = 8 - valence electrons

So, for the given elements -
$$\begin{array}{cccc}\text{Element}& \text{Atomic no.}& \text{Electronic configuration}& \text{Valency}\\ \text{Lithium}& \text{3}& \text{2, 1}& \text{1}\\ \text{Beryllium}& \text{4}& \text{2, 2}& \text{2}\\ \text{Boron}& \text{5}& \text{2, 3}& \text{3}\\ \text{Carbon}& \text{6}& \text{2, 4}& \text{4}\end{array}$$