Question

Which halide of titanium has the highest melting point?
A. $\text{TiC}{{\text{l}}_{2}}$
B. $\text{TiC}{{\text{l}}_{3}}$
C. $\text{TiC}{{\text{l}}_{4}}$
D. All have the same melting point

Answer 1

The melting point of a structure depends on various factors such as the bond present between the atoms, more strong is the bond more will be its melting point. Thallium chloride has a melting of $1035{}^\circ \text{C}$ whereas that of thallium trichloride and thallium tetrachloride is $425{}^\circ \text{C and }25{}^\circ \text{C}$.

Complete answer:
-To identify the molecule with a higher melting point, we have to study the type of bond present between the atom and how strong they are.
-Those atoms which are bonded with a strong bond have a higher melting bond because the energy needed to break them will be higher.
-Now, the melting of thallium tetrachloride is the lowest because the bond present between the atoms is Vander Wall bond which is the weakest and needs less energy to break.
-Moreover, the effective nuclear charge on each bond is less as compared to the thallium chloride and thallium trichloride.
-Now, in thallium trichloride the bond is metallic and also the length of the bonds is smaller as compared to that of the thallium tetrachloride.
-That’s why $\text{TiC}{{\text{l}}_{3}}$ has a higher melting point than $\text{TiC}{{\text{l}}_{4}}$.
-Now, similarly in $\text{TiC}{{\text{l}}_{2}}$ the length of the bond is smaller than the thallium trichloride and hence, needs more energy to break the bond.

Therefore, option A is the correct answer i.e. $\text{TiC}{{\text{l}}_{2}}$ has a higher melting point.

Note: Melting point of any substance is the point at which the substance changes from solid-state to the liquid state. The ionic bond is usually more than the covalent bond because in the ionic bond the electrostatic interaction is present which is most strong. Melting point is also affected by the presence of the impurities.