Advanced Placement (AP) Chemistry Practice Exam

What is meant by a network covalent bond?

1. A bond with a single pair of shared electrons

2. A lattice of covalent bonds acting like a single molecule

3. A bond formed between two metals in a solid state

4. A bond that is poorly conducting and low in melting point

The correct answer is: A lattice of covalent bonds acting like a single molecule

A network covalent bond refers to a structure in which atoms are bonded covalently in a continuous network. In this arrangement, the entire solid is essentially one large molecule made up of a repetitive network of covalent bonds. This type of bonding occurs in materials like diamond and silicon carbide, where each atom is connected to its neighbors through strong covalent bonds, resulting in a rigid and stable structure. The significance of this network structure is that it leads to unique physical properties. Unlike molecular compounds, which can consist of distinct, separate molecules, network covalent compounds do not have discrete molecules; instead, they form a solid lattice of interconnected atoms. This bonding contributes to high melting points and hardness, as breaking these covalent bonds requires significant energy. In contrast, the other options describe different types of bonding or properties that do not align with the concept of network covalent bonding. For example, a single pair of shared electrons describes a simple covalent bond rather than a network, while metallic bonds typically involve a sea of electrons and lattice structures of metals, which do not classify as network covalent. A poorly conducting material with a low melting point refers more to covalent molecular substances rather than the robust network we associate with network covalent compounds.