Which characteristic of metals allows them to be shiny?

The characteristic of metals that allows them to be shiny is primarily related to the arrangement of electrons. In metals, the outer electrons are loosely bound and can move freely within the metal lattice. This "sea of electrons" can interact with light, reflecting it and giving metals their characteristic luster. When light strikes a metal's surface, these delocalized electrons can absorb and re-emit the light, producing a shiny appearance.

While the other choices mention various properties of metals, they do not directly explain why metals exhibit a shiny, reflective quality. High melting points reflect the strong metallic bonds but do not relate to the shininess. Electron configuration refers to the arrangement of electrons in energy levels but doesn’t specifically encompass their movement and interaction with light. The ability to donate electrons is indicative of metallic bonding and conductivity, but again does not explain the shiny appearance. The arrangement and mobility of electrons are the key factors that result in metals appearing shiny.