What kind of forces arise from transient dipoles in atoms that induce transient dipoles in nearby atoms, produce an attractive force and are significant only over short distances (~500 pm)?

Question

Question

This question was previously asked in

SSC CGL 2022 Tier-I Official Paper (Held On : 02 Dec 2022 Shift 1)

Answer 1

The correct answer is London dispersion forces.

Key Points

Atoms and nonpolar molecules are electrically symmetrical and have no dipole moment because their electronic charge cloud is symmetrically distributed. But a dipole may develop momentarily even in such atoms and molecules.
This force of attraction was first proposed by the German physicist Fritz London, and for this reason force of attraction between two temporary dipoles is known as the London force.
These forces are always attractive and interaction energy is inversely proportional to the sixth power of the distance between two interacting particles (i.e., 1/r 6 where r is the distance between two particles)
These forces are important only at short distances (~500 pm) and their magnitude depends on the polarisability of the particle.

londn

Additional Information

Dipole-dipole forces
- Dipole-dipole forces act between the molecules possessing permanent dipole. Ends of the dipoles possess “partial charges” and these charges are shown by the Greek letter delta (δ)
- The polar molecules interact with neighboring molecules.
- This interaction is stronger than the London forces but is weaker than ion-ion interaction because only partial charges are involved.
Dipole–Induced Dipole Forces
- This type of attractive force operates between the polar molecules having permanent dipole and the molecules lacking permanent dipole.
- The permanent dipole of the polar molecule induces a dipole on the electrically neutral molecule by deforming its electronic cloud.
- Thus an induced dipole is developed in the other molecule.
- Induced dipole moment depends upon the dipole moment present in the permanent dipole and the polarisability of the electrically neutral molecule.
Hydrogen bond
- This is a special case of dipole-dipole interaction found in the molecules in which highly polar N–H, O–H or H–F bonds are present. Although hydrogen bonding is regarded as being limited to N, O and F; species such as Cl may also participate in hydrogen bonding