The molecular lattice of iodine is held together by

Analysis

The question asks for the type of intermolecular force responsible for holding the molecular lattice of iodine ($I_2$) together.

Concept Explanation

Iodine is a non-metal that exists as a diatomic molecule ($I_2$). In its solid state, iodine forms a molecular crystal lattice. To understand what holds this lattice together, we look at the nature of the molecules:

1. Non-polar nature: Iodine molecules are non-polar because the two iodine atoms share electrons equally.
2. Intermolecular forces: Since the molecules are non-polar, they do not experience strong electrostatic attractions like ionic or covalent bonds. Instead, they are held together by weak van der Waals forces (specifically, London dispersion forces). These forces arise from temporary fluctuations in electron distribution, creating temporary dipoles that induce dipoles in neighboring molecules.

Step-by-Step Solution

1. Identify the structure: Iodine ($I_2$) is a molecular solid.
2. Evaluate the bonds: • Covalent bonds: These exist within the $I_2$ molecule (holding the two iodine atoms together), but not between the molecules in the lattice. • Metallic bonds: These only occur in metals (e.g., iron, copper), which iodine is not. • Hydrogen bonds: These require a hydrogen atom bonded to a highly electronegative atom (N, O, or F). Iodine does not meet this criteria. • Van der Waals forces: These are the weak attractive forces that exist between neutral, non-polar molecules.
3. Conclusion: Because the iodine molecules are non-polar and neutral, the only forces strong enough to hold them in a lattice structure at room temperature are van der Waals forces.

Correct Option

The correct option is D.

Exam Tip

Whenever you see questions about the physical properties of non-polar molecular solids (like Iodine, $CO_2$, or Naphthalene), remember that they generally have low melting points and are held together by van der Waals forces. If the question asks about the bond inside the molecule, it is a covalent bond; if it asks about the force between the molecules in the lattice, it is van der Waals forces.