Question

Give the important physical characteristics of halogens.

Answer 1

1. Physical state: Fluorine and chlorine are gases at room temperature, bromine is a liquid, while iodine is a solid.
2. Atomic and ionic radii: A halogen atom has the smallest atomic radius in its period. As one moves down the group, the atomic and ionic radii get larger.
3. Density: Moving down the group causes the density of halogens to grow. This results from a rise in the agglomeration state.
4. Melting and boiling points: The melting and boiling points of halogens are low. As one moves along the group, the melting and boiling points rise.
5. Ionisation energy: Halogens have very high ionisation energies. As one moves along the group, the ionisation energies decrease.
6. Electronegativity: The electronegativity of halogens is extremely high. Each halogen is actually the most electronegative element in its time period. As you go down the group, the electronegative values drop.
7. Electron gain enthalpy: The electron gain enthalpy values of halogens follow the following trends.
   1. Halogens have maximum negative values of electron gain enthalpy.
   2. The negative electron gain enthalpy of fluorine is unexpectedly lower than that of chlorine.
   3. The negative electron gain enthalpy values decrease from Cl to I.
8. Non-metallic character: All halogens are considered typical non-metals because of their strong electronegativity. Even for astatine, the final member of the group, there is no indication of any metallic behaviour. Iodine, on the other hand, has a minor metallic character in that it has a metallic lustre and, under certain circumstances, has a tendency to produce monopositive (I⁺) and tripositive (I³⁺) ions due to a decrease in electronegativity down the group.
9. Oxidation states: In all of its compounds, fluorine only shows the oxidation state of −1. The compounds of the other halogens have oxidation states of −1, +1, +3, +5, and +7.
10. Colour: All the halogens are coloured. The colour darkens on moving down the group.