Question

Which is more covalent $LiF$ or $LiCl$?

Answer 1

We need to know that the covalent character of a molecule can be determined by using electronegativity. When the molecule has greater electronegativity, the bond is ionic and if the molecule has smaller electronegativity, the molecule creates more covalent character. The covalent bond is a chemical bond which is formed by sharing the pair of electrons between two atoms. And these shared electrons are called bonding pairs.

Complete answer:
As we know that among the given compounds, lithium chloride $\left( {LiCl} \right)$ is more covalent than the lithium fluoride due to the size of the anion and cation present in the given compounds. According to the Fajan’s rule, the size of anion present in the lithium chloride is larger than the cation. When the size of the cation decreases, the polarizing power will increase. Therefore, the covalent character of lithium chloride is larger than lithium fluoride.
Most of the lithium compounds are always covalent in nature due to its small size. Lithium belongs in group one and its atomic number is three. Hence, lithium is the smallest atom present in the periodic table. Due to its smaller size, the attraction between nucleus and the outer electrons is very high. Therefore, it requires more energy to lose the outer electrons to another element for the formation of a compound with an ionic bond.

Note:
As we know that the covalent bond is formed by sharing the pair of electrons. The lithium chloride is more covalent than lithium fluoride due to its size of cation and anion. Among the alkali metals, the size of lithium is very small. Hence, it is very hard to remove the outer electrons to another element by forming an ionic bond. The polarizing power of lithium chloride is also very less.