The weakest attractive force that can be observed between two molecules is

Analysis

The question asks us to identify the weakest type of attractive force among the options provided. To answer this, we must compare the relative strengths of chemical bonds and intermolecular forces.

Concept Explanation

In chemistry, forces of attraction are generally categorized into two groups:

1. Intramolecular forces (Chemical Bonds): These are the forces that hold atoms together within a molecule. They are very strong. Examples include: • Ionic bonds: Electrostatic attraction between oppositely charged ions. • Covalent bonds: Sharing of electron pairs between atoms. • Co-ordinate covalent (Dative) bonds: A type of covalent bond where both electrons come from one atom.

2. Intermolecular forces: These are the forces of attraction between separate molecules. They are significantly weaker than chemical bonds. Van der Waals forces are the weakest of these intermolecular forces. They arise from temporary fluctuations in electron distribution, creating temporary dipoles.

Step-by-Step Solution

1. Evaluate Options A, B, and C: Ionic, Covalent, and Co-ordinate covalent bonds are all strong chemical bonds. They require a significant amount of energy to break because they involve the transfer or sharing of electrons to achieve stable electronic configurations.
2. Evaluate Option D: Van der Waals forces are weak, short-range electrostatic attractions between molecules. Because they depend on temporary or induced dipoles, they are easily disrupted by thermal energy.
3. Comparison: Since Van der Waals forces are intermolecular and the others are intramolecular, Van der Waals forces are significantly weaker than the bonds listed in A, B, and C.

Conclusion

The weakest attractive force among the choices is the Van der Waals force.

Exam Tip

Remember the hierarchy of strength: Ionic > Covalent > Hydrogen Bonding > Van der Waals. If you ever forget, think about the state of matter: substances held together by Van der Waals forces (like noble gases or non-polar molecules) usually have very low melting and boiling points because the forces are so easy to overcome!