Humber Admissions Practice Test

Why do nonmetals typically have poor conductivity?

1. They are brittle and dull

2. They lack free electrons

3. They are often liquids

4. They have high melting points

The correct answer is: They lack free electrons

Nonmetals typically have poor conductivity primarily because they lack free electrons. In conductive materials, such as metals, electrons can move freely, forming an 'electron sea' that allows for the efficient transfer of electrical current. Nonmetals, in contrast, do not possess this abundant supply of free electrons. Instead, their atomic structure holds onto electrons more tightly, which inhibits the flow of electrical current. This inherent property results in nonmetals being poor conductors of electricity. Regarding the other options, while some nonmetals can be brittle or dull, these characteristics do not directly influence their ability to conduct electricity. The state of being a liquid does not necessarily correlate with conductivity, as many liquids (like saltwater) can conduct electricity due to dissolved ions. Lastly, while high melting points can be characteristic of some nonmetals, this attribute is more related to their stability at elevated temperatures than to their conductivity. Thus, the factor most directly influencing poor conductivity in nonmetals is the absence of free-moving electrons.