Question

Define van der Waal’s radius of an atom.

Answer 1

The Van der Waal's radius is half the distance between two unbonded atoms when the electrostatic forces are balanced between them.  

The dimensions of Van Der Waal's forces are Picometers (pm).

The distance between two atoms reflects the action of intermolecular forces(e.g. dipole and dispersion forces) and is linked to the interactions between Van der Waals. Vander Waals radius is helpful in predicting the distance between two atoms which are lies in the solid.

Answer 2

The van der Waals constant 'a' represents the magnitude of intermolecular forces of attraction and the Van der Waals constant 'b' represents the effective size of the molecules.