Which is a property of metals that contributes to their conductivity?

Metals are known for their excellent electrical and thermal conductivity, which is primarily attributed to the presence of loosely held outer electrons. In metallic bonds, the outermost electrons of metal atoms are not tightly bound to individual atoms; instead, they can move freely within the metal lattice. This phenomenon is often referred to as the "sea of electrons."

When an electric field is applied, these free electrons can drift and carry charge through the metal, which is the fundamental mechanism behind electrical conductivity. Additionally, these loosely held electrons also facilitate the transfer of thermal energy, which contributes to metals being good thermal conductors as well.

In contrast, properties like low melting points, high atomic weight, and high density do not directly relate to the electrical or thermal conductivity of metals. Therefore, the ability of metals to conduct electricity and heat is significantly enhanced by the mobility of their outer electrons, making this property foundational for understanding metal behavior in various applications.