What is a defining characteristic of non-metals compared to metals?

Non-metals are characterized by their generally poor conductivity of both heat and electricity. This is a fundamental distinction between non-metals and metals. Metals are typically good conductors due to their ability to allow electrons to flow freely within their structure. In contrast, non-metals lack this property; they do not have free electrons to facilitate conduction, making them insulators in most cases.

This difference in conductivity is evident in various forms, such as when comparing substances like sulfur or phosphorus (which are non-metals) to copper or aluminum (which are metals). Non-metals often take on different states at room temperature (like gases or solids) and have varying properties that differ greatly from those of metals, further emphasizing the contrast in their electrical and thermal conductivity.