I'm an A-level student and I love learning new things in physics. A new concept that I learnt says that the reflection is due to the scattering of light by electrons in the material. I've got my head around this yet something that bothers me is how do shiny surfaces like a mirror or reflective surface like silver or platnum reflect almost all of the light that it receives and yet certain other metals don't. If it depends on the electrons scattering light, why is the material or composition of electrons so important? What is the property that makes reflective surfaces the way that they are even when the number of electrons differs?
A clean metallic surface appears shiny because it is reflecting light. The interaction is due to the conductivity of the surface of the metal.
When surface conditions change, the reflectivity is reduced. For example, a clean aluminum surface is very reflective, and aluminum coatings are used on the back side of mirrors; the glass protects the clean aluminum surface.
If the clean aluminum surface is exposed to air it will rapidly oxidize. You can test this by scratching or cutting any thick piece of dull aluminum. The oxidized layer is actually a good insulator, but is quite thin. The same holds for most other metals. If they don't tarnish, then stuff gets on the surface.