TeXes Science Practice Test

Which characteristic of covalent compounds contributes to their poor conductivity of heat?

1. Absence of metallic bonds

2. The presence of free electrons

3. High density and compactness

4. Lack of free electrons

The correct answer is: Lack of free electrons

Covalent compounds are typically formed when atoms share electrons to achieve stability, resulting in the formation of molecules. One of the key characteristics that contribute to their poor conductivity of heat is the lack of free electrons. In conductive materials, such as metals, free electrons can move easily throughout the material, allowing them to carry thermal energy efficiently. This is not the case in covalent compounds, which do not have free electrons available for conduction. Instead, the electrons are localized within the bonds between specific atoms, restricting their movement. As a result, covalent compounds cannot transfer thermal energy effectively among their particles. The absence of metallic bonds further emphasizes the difference, as metallic states allow for a "sea of electrons" that facilitates conduction. While high density and compactness can be features of some covalent compounds, they do not directly influence their ability to conduct heat in the same manner as the presence or absence of free-moving electrons.