Final answer:
Luster refers to how a mineral's surface reflects light, with metallic luster indicating no light passing through and non-metallic allowing some. Metals exhibit high luster due to free electrons that facilitate light reflection. Nonmetals generally lack luster and are poor conductors, appearing dull.
Step-by-step explanation:
The correct definition of Luster is 'the way that the surface of a mineral reflects light.' Luster can be either metallic or non-metallic, indicating whether a surface appears similar to a metal or not. Minerals with metallic luster do not allow light to pass through their atomic structure, whereas non-metallic minerals do allow some light through. This characteristic luster is evident because when light shines on a metal surface, its electrons absorb and immediately re-emit light, leading to the metal's shiny appearance.
Metals, characterized by properties such as shiny appearance, malleability, ductility, and the ability to conduct heat and electricity efficiently, are described as being lustrous. This is due to the presence of free-floating electrons within the metal's atomic structure, which allows for the efficient transfer of heat and electricity and results in a high luster.
On the other hand, nonmetals typically lack luster, are brittle, and are poor conductors of heat and electricity. They can exist in various states at room temperature and pressure, including gases, liquids, and solids, and do not reflect light in the same way as metals.