What is the main property that distinguishes metals from nonmetals?

The main property that distinguishes metals from nonmetals is electrical conductivity. Metals are known for their ability to conduct electricity efficiently due to the presence of free-moving electrons within their structure. This characteristic is a result of their atomic structure, which allows for the delocalization of electrons. As a result, when a voltage is applied, these electrons can move freely, allowing metals to effectively conduct electrical current.

While thermal conductivity, malleability, and luster are also properties that are typically associated with metals, electrical conductivity is the most defining characteristic that differentiates metals from nonmetals. Nonmetals, in contrast, do not possess the same level of free-moving electrons, which contributes to their significantly lower levels of electrical conductivity. Many nonmetals are insulators or semiconductors, which limits their ability to conduct electricity compared to metals.