Question

Why are metals lustrous?
A. Light is transmitted through delocalized electrons
B. They have a high boiling point
C. Light is reflected through delocalized electrons
D. Light does not travel through metals at all.

Answer 1

Hint: It has to do with the way light and free electrons present on a metal surface interact and can be easily answered by the electron sea model of a metal atom.

Complete step by step solution:
Generally, properties of bulk metals arise from their structure, which is a unique and third kind of bonding called “metallic” (after “covalent” and “ionic”).
1. Out of all typical properties of metals, one is that metals are lustrous. Metals are lustrous due to the flow of free electrons.
2. The outer electrons in a metal are almost not bound to any individual atom, thus are relatively free.
3. These free electrons (electron density) are concentrated on the surface and can move freely in metal. They tend to oscillate at a collective frequency.
4. As they oscillate they prevent any incoming light from entering the metal or transmitting through it.
5. Consequently, the incident light is reflected back. Although a lot of materials also reflect, only those with a lot of nearly free electrons can reflect huge amounts of light.
6. It is the intensity of this reflected light reaching our eyes that make it appear lustrous.

There from above points we can conclude that option C is the correct option.

Additional information:
Other properties of metals which arise due to their unique structure and metallic bonding are as follows:
Metals have very high boiling point.
They have the ability to be drawn into thin wires.
Metals have the ability to be hammered into very thin sheets.
They are good conductors of heat and electricity due to the presence of free electrons.
They possess high tensile strength.

Note: It should be remembered that as the metal surface comes in contact with the environment it forms oxides which restrict the mobility of free electrons. Thus, in this case we have diffused reflection and the surface of metal appears dull.