A Level Chemistry OCR Practice Exam

What characterizes a simple molecular lattice?

1. A three-dimensional structure of ions bonded by strong ionic bonds

2. A structure of molecules bonded together by weak intermolecular forces

3. A two-dimensional arrangement of atoms in a solid

4. A complex network of covalently bonded atoms

The correct answer is: A structure of molecules bonded together by weak intermolecular forces

A simple molecular lattice is characterized by a structure of molecules that are bonded together by weak intermolecular forces, such as Van der Waals forces or hydrogen bonds. In this type of lattice, the fundamental units are discrete molecules held together in a regular three-dimensional arrangement. These weak forces allow the molecules to remain close to one another while still being able to slide past each other relatively easily, giving materials like ice or solid carbon dioxide their characteristic properties. The other answer choices describe different types of bonding or arrangements that do not apply to simple molecular lattices. For example, structures with strong ionic bonds are typical of ionic lattices, which have a very different stability and melting point compared to those held by weaker intermolecular forces. A two-dimensional arrangement typically refers to structures like graphene, which does not encapsulate the three-dimensional space seen in simple molecular lattices. Lastly, a complex network of covalently bonded atoms describes covalent networks, where atoms are bonded in a continuous framework, like diamond or silicon dioxide, diverging significantly from the molecular structures that a simple molecular lattice embodies.