Which substance is an example of a giant molecular structure?

• A. Silicon dioxide
• B. Sodium chloride
• C. Nitrogen gas
• D. Methane

Answer: (A)

A giant molecular structure is a solid where atoms are linked by a continuous network of covalent bonds throughout the material, forming a 3D lattice. Silicon dioxide does this: each silicon atom is covalently bonded to four oxygen atoms, and these bonds extend in all directions to create a single, continuous framework. This gives it properties like a very high melting point and great hardness, and it doesn’t conduct electricity because there are no free charged particles.

The other options don’t form such a covalent network. Nitrogen gas is made of individual N2 molecules with strong bonds between two atoms, but these molecules do not connect into a network. Methane consists of discrete CH4 molecules held together by weak intermolecular forces, not a continuous network. Sodium chloride is an ionic lattice held together by electrostatic forces between ions, not covalent bonds. Hence, silicon dioxide best represents a giant molecular (covalent network) structure.