Question

Which of the following properties of elements - $Cl,Br,andI$ increase(s) with the increase in atomic number?

• A. Enthalpy of vapourization
• B. Ionic radius
• C. Bond energy of the molecule $X_2$
• D. Ionization energy

Answer 1

Answer: (A), (B)

Ionic radius

As we go down the group, ionic radius definitely increases. But what about the intermolecular forces?

The magnitude of the intermolecular forces increases with the increase in the molar mass of the molecule. As we go down the group, the number of electrons increase and the atoms/molecules become more polarizable because of the increasing size of the electron cloud. The overall effect is that in the liquid phase, as we go down the group (chlorine is a gas though), the enthalpy of vapourization will increase.