Final answer:
Metals shine and have luster because they reflect light well due to the free movement of electrons within their structure, not because of increased density, hardness, or reactivity.
Step-by-step explanation:
The reason metals are lustrous and shine, especially when they are freshly cut, is shine because of increased reflectivity. Metals are shiny due to their ability to reflect light well; this reflective property gives metals their characteristic luster. When light interacts with the surface of a metal, the free electrons in the metal absorb and re-emit the light, causing the metal to appear shiny. This happens because in metallic bonds, electrons are delocalized, which means they are free to move throughout the metal. This allows for the electrons to interact with light and reflect it efficiently. The luster of a metal is not due to its density, hardness, or reactivity; it is purely a function of how the metal's electron structure interacts with light.
The physical properties of metals, such as their ability to conduct electricity and heat, malleability, and ductility, are also explained by the nature of metallic bonds. While freshly cut metals will shine due to their smooth, clean surface allowing for optimal reflection, the underlying cause of this shine is the metal's inherent reflective properties due to its electron structure.