Question

Which is more covalent $MgC{l_2}$ or $AlC{l_3}$?

Answer 1

Hint: We have to know $MgC{l_2}$ and $AlC{l_3}$ are ionic compounds. These ionic compounds contain ionic bonds. We have to know that the formation of an ionic compound occurs when the electrons are donated by an atom and those electrons are accepted by other atoms. Strong electrostatic forces of attraction hold these ions together.

Complete answer:
In an ionic compound, the ions which are positively charged are called cations and the ions which are negatively charged are called anions. We have to know that for an ionic compound, the overall charge on an ionic compound is neutral.
In ideal circumstances we can say that a bond is hundred percent ionic or covalent in nature. Yet, in actuality, no bond is totally ionic or covalent. If we take an example of the covalent hydrogen atom, some ionic characters will be noticed. There is an incomplete presence of covalent characters in an ionic bond which is talked about by Fajans in the accompanying principle.
The distinction in the size of the particles will decide the level of covalent character in the ionic bond. For instance, if the size of the cation is little and that of the anion is huge. The ionic bond will show more covalent characters.
The more prominent the charge present on the cation more will be the covalent character of the ionic bond.
The cations which have little size and charge like that of the progress metals with electronic arrangement \[\left( {n - 1} \right){\text{ }}{d^n}{\text{ }}n{s^0}\]are more polarizing in nature when contrasted with the cations having honorable gas electronic setup \[n{s^2}{\text{ }}n{p^6}\](like salt or soluble earth metals).
Now, let us determine which is more covalent $MgC{l_2}$ or $AlC{l_3}$
We saw that covalent character and cationic size are indirectly related to each other. In simple words, we can say when the size of the cations is smaller; the covalent character would be higher. In $MgC{l_2}$, the cation is $M{g^{2 + }}$ and in $AlC{l_3}$, the cation is $A{l^{3 + }}$. We have to know that the size of $M{g^{2 + }}$ is larger when compared to the size of $A{l^{3 + }}$. So, the covalent character of $AlC{l_3}$ is more.
The compound that has higher covalent character is $AlC{l_3}$.

Note:
We can say that when the size of cation is smaller, the charge density would be higher. Due to more charge density, the polarization would also be more. As the polarization is more, the covalent character would also be higher.