Question

Which is more covalent LiCl or CsCl?

Answer 1

Hint :Covalent character if a molecule is detected by using Fajan’s rule. The rule can be based on: (i) Size of the ion (ii) Charge of cation (iii) Electronic configuration. The first and the second rule are the most applied to find the covalent character of an atom.

Complete Step By Step Answer:
If the size of the anion (negatively charged) is bigger than the cation (positively charged) then the covalent character is greater. Also, if the charge on the cation is greater the covalent character is more.
In LiCl (Lithium Chloride) and CsCl (Cesium Chloride),
Chlorine is the anion and lithium and cesium are cations as non-metals tend to gain electrons and metals tend to lose electrons.
Applying rule (i) we get to know that if the cation is smaller than the charge density on the cation will be more. The high charge density will increase the polarising power of the molecule. Thus, the compound will be more covalent.
In LiCl and CsCl, Lithium is a smaller cation than Cesium. This increases the charge density of lithium. Also, rule (ii) states that more charge on the cation more is the covalent character. Lithium has more charge than Cesium.
Therefore, LiCl is more covalent than CsCl.

Note :
Always remember not only the charge but the size of the cation also affects the covalent character. If the size of the cation increases the covalent character of the compound decreases. For the chloride compounds of Alkaline earth metals, the decreasing order of covalent character is LiCl > NaCl > KCl > RbCl > CsCl.