Question

The correct sequence of increasing covalent character is represented by:
(A) $\text{BeC}{\text{l}}_{\text{2}}\text{ < NaCl < LiCl}$
(B) $\text{NaCl}<\text{LiCl}<\text{BeC}{\text{l}}_{\text{2}}$
(C) $\text{BeC}{\text{l}}_{\text{2}}\text{ < LiCl < NaCl}$
(D) $\text{LiCl}<\text{NaCl}<\text{BeC}{\text{l}}_{\text{2}}$

Answer 1

Hint:
A covalent bond also has a partial ionic character to it due to the difference in electronegativity between the two bonding atoms. More is the electronegativity difference, the more will be the ionic character and due to this the lesser will be the character and due to this the lesser will be the covalent character. However, the covalent character is the measure of the ability of an atom to attract a shared pair of electrons towards itself.

Complete step by step answer:
As we know that, the covalent bond is formed when the electrons are being mutually shared between the two bonds and thus we can say that the covalent character is the measure of the tendency of an atom to attract the shared pair of electrons towards itself.
Now, we know that the covalent character depends on the electronegativity difference as the smaller the difference of electronegativity between the atoms, the more will be the covalent character of the bond and the large the difference in the electronegativity of the two bonded atoms, the lesser will be the covalent character of the bond between them.
We already know that the electronegativity values do increase from left to right across the periodic tables whereas the electronegativity values do decrease from the top to the bottom within a group of elements in the periodic table.
Here, in the given question, for determining the order of the covalent character, firstly we need to know the electronegativity difference between the atoms of given bonds.
Since, the element chlorine $\left(Cl\right)$ is common in all the given bonds. We thus, only need to know the electronegativity value of the atoms bonded to chlorine. So that, we can easily compare the given bonds with each other for determining the covalent character.
As mentioned earlier, the electronegativity values increase across a period that means the electronegativity value of $Be$ would be more than $Li$and due to the decrease in the electronegativity value across a group, the $Na$will have less electronegativity value than $Li$. The order of electronegativity can be written as:
$Na<Li<Be$
Therefore, the covalent character would increase in the order as: $NaCl<LiCl<BeC{l}_2$
Hence, the correct answer is option (B).

Note: The less the covalent character in a bond means the more will be the ionic character. Thus, we can also say that, the more is the electronegativity difference, the more will be the ionic character and due to this the lesser will be the character and due to this the lesser will be the covalent character and vice versa.