Non-polar molecules are held together by

Step 1: Analyze the question The question asks about the force that holds non-polar molecules to one another. These are the attractions between separate molecules (intermolecular forces), not the bonds inside a molecule.

Step 2: Explain the concept

• Covalent bonds (and co-ordinate bonds) hold atoms together within a molecule. They are intramolecular.
• Hydrogen bonds need a hydrogen atom attached to a very electronegative atom (N, O or F). Non-polar molecules like O₂, N₂, CH₄ and I₂ don't have this.
• Van der Waals forces are weak intermolecular attractions caused by temporary (instantaneous) dipoles. In a non-polar molecule, the electrons can shift momentarily and create a brief dipole, which induces a dipole in a neighbouring molecule. This produces a weak attraction. These are also called London dispersion forces.

Step 3: Apply to the options

• A. Co-ordinate bond: occurs within molecules/ions (e.g. NH₄⁺), so it's not the answer.
• B. Covalent bond: holds atoms within a molecule, so it's not the answer.
• C. Electromagnetic force: this is not the term used in chemistry for bonding between molecules.
• D. Hydrogen bond: requires polar H–N/O/F bonds, so it's not the answer.
• E. Van der Waals forces: correct. They are the only attractions between non-polar molecules.

Step 4: Answer Non-polar molecules are held together by Van der Waals forces, which is option E. This also explains why non-polar substances like iodine, methane and naphthalene have low melting and boiling points and are often volatile or easily sublimed.

Exam tip: Remember "bonds hold atoms, forces hold molecules." If a question asks what holds non-polar molecules together, think Van der Waals. For water, HF and NH₃, think hydrogen bonding.