What causes the high luster of a metal? a excitation of electrons into empty orbitals b mobility of electrons C easily ionizable metal atoms d their low melting points
The Correct Answer and Explanation is:
Correct Answer: B. mobility of electrons
Explanation
The high luster of a metal arises from the mobility of electrons, specifically the behavior of the delocalized electrons found within the metallic structure. In a metallic bond, atoms release some of their electrons to form a “sea of electrons” that is free to move throughout the entire structure. This electron sea is not bound to any one atom and is highly mobile.
When light strikes the surface of a metal, the free electrons in this sea absorb and re-emit the light almost instantly. This process is known as reflection, and it gives metals their characteristic shiny appearance, or luster. The re-emission of light occurs because the electrons are free to oscillate and respond to incoming electromagnetic radiation. These oscillations match the frequency of the incident light, allowing it to reflect off the surface efficiently.
This phenomenon is especially prominent in metals due to the absence of a band gap between the valence band and conduction band. The energy levels in metals overlap, permitting electrons to move freely and respond to external energy inputs, including visible light. This interaction results in the surface of the metal reflecting most of the light rather than absorbing it, which enhances the luster.
In contrast, nonmetals lack this electron mobility. Their electrons are more tightly bound to individual atoms or molecules, and as a result, light tends to be absorbed or transmitted rather than reflected. This explains why nonmetallic materials generally appear dull or transparent.
Therefore, the unique arrangement of metallic atoms and the presence of a delocalized electron cloud allow metals to reflect light uniformly, leading to their high luster. This characteristic is one of the defining physical properties of metals and is directly tied to the nature of metallic bonding and electron mobility within the structure.
