Which of the following compounds is an example of a network solid?

• A. CO_2 (dry ice)
• B. H_2O (ice)
• C. NaCl (table salt)
• D. SiO_2 (quartz)

Answer: (D)

Verified step by step guidance

1. Understand what a network solid is: a type of solid where atoms are bonded covalently in a continuous, extended three-dimensional network, rather than existing as discrete molecules or ions.
2. Analyze each compound's bonding and structure: CO_2 (dry ice) consists of discrete molecules held together by weak intermolecular forces; H_2O (ice) also consists of molecules connected by hydrogen bonds, which are intermolecular forces, not covalent bonds forming a network.
3. Consider NaCl (table salt), which is an ionic solid composed of a lattice of alternating Na^+ and Cl^- ions held together by ionic bonds, not covalent network bonds.
4. Examine SiO_2 (quartz), which is composed of silicon and oxygen atoms covalently bonded in a continuous three-dimensional network, making it a classic example of a network solid.
5. Conclude that among the given options, SiO_2 (quartz) is the network solid because of its extended covalent bonding throughout the structure.