Question

The electronegativity of halogens decreases from fluorine to iodine while the electron affinity has the trend ${\text{Cl > F > Br}}{\text{ > I}}$. The halogens are good oxidizers The oxidizing power of halogens in aqueous medium depends on their electron affinity, bond dissociation energy and heat of hydration. Basic character of their anions depends on their size and electronegativity. Similarly, the ionic character of the salts of different halides of the same metal depends on their electronegativity and size. The heat of hydration and the basic character of halide ions follow the order:
a.) ${\text{C}}{{\text{l}}^{ - 1}}{\text{ > }}{{\text{F}}^{ - 1}}{\text{ > B}}{{\text{r}}^{ - 1}}{\text{ > }}{{\text{I}}^{ - 1}}$
b.) ${{\text{F}}^{ - 1}}{\text{ > C}}{{\text{l}}^{ - 1}}{\text{ > B}}{{\text{r}}^{ - 1}}{\text{ > }}{{\text{I}}^{ - 1}}$
c.) ${{\text{I}}^{ - 1}}{\text{ > B}}{{\text{r}}^{ - 1}}{\text{ > }}{{\text{F}}^{ - 1}}{\text{ > C}}{{\text{l}}^{ - 1}}$
d.) ${{\text{I}}^{ - 1}}{\text{ > B}}{{\text{r}}^{ - 1}}{\text{ > C}}{{\text{l}}^{ - 1}}{\text{ > }}{{\text{F}}^{ - 1}}$

Answer 1

Hint: Halogens are elements while halides are substances that are ionically bonded. These are essentially the salts formed by halogen atoms and hydrogen atoms.

Complete step-by-step answer:
As we know, smaller the size of the element greater will be the hydration of the halide ion. To confirm the same, firstly we can check the covalent radius of fluorine as 72, chlorine as 99, bromine as 114 and iodine as 133. We can also check the Ionic radius fluorine as 133, chlorine as 184, bromine as 196 and iodine as 220. Here we can clearly see that fluorine is the smallest of all other halogens and the following trend goes like chlorine, bromine and Iodine in increasing order of their covalent and ionic radii.

$\therefore {\text{ F < Cl < Br}}{\text{ < I}}$

To verify that smaller size elements have greater hydration, we can see the heat of hydration for halogens starting from fluorine to iodine in ${\text{kJ mo}}{{\text{l}}^{ - {\text{1}}}}$ are, fluorine having 510 ${\text{kJ mo}}{{\text{l}}^{ - {\text{1}}}}$, chlorine having 372 ${\text{kJ mo}}{{\text{l}}^{ - {\text{1}}}}$, bromine having 359 ${\text{kJ mo}}{{\text{l}}^{ - {\text{1}}}}$ and iodine having 301 ${\text{kJ mo}}{{\text{l}}^{ - {\text{1}}}}$. Hence, we can see that the heat of hydration of fluorine to iodine starts decreasing from fluorine and is lowest in iodine in terms of ${\text{kJ mo}}{{\text{l}}^{ - {\text{1}}}}$. It can be written as:

${\text{F > Cl > Br}}{\text{ > I}}$

Now, the basic character of halide ions can be determined by the theory that the strongest acid has the weakest conjugate base. Hence, HF which is the weakest acid has fluorine as the strongest base and iodine as the weakest base. Therefore, we can conclude that the order of strong basicity of halogen atoms goes as,

${{\text{F}}^{ - 1}}{\text{ > C}}{{\text{l}}^{ - 1}}{\text{ > B}}{{\text{r}}^{ - 1}}{\text{ > }}{{\text{I}}^{ - 1}}$

Note: Halogens tend to display the physical and the chemical properties which are quite similar to that of the non metals. The relative low melting point and boiling point which increases steadily down the group makes them quite similar to that of the nonmetals.
All the members of the halogen family consist of seven valence electrons as it is already mentioned in the answer. Because these atoms are so close to having a full set of eight valence electrons they are very reactive. They always show a tendency to gain one electron by forming bonds and then take the electrons from the other atoms to attain the octet configuration.