Question

A lustrous non-metal is?

Answer 1

Luster is the property of any element to impart shine. This property of imparting shine and being lustrous is mainly a characteristic property exhibited by metals. They impart shine due to the free electrons that are present in their crystal lattice.

Complete answer: Non-metals exhibit the properties as the opposite to that of metals, that is:
- Non-metals are not hard, brittle or lustrous.
- Non-metals are not malleable or ductile.
- Non-metals are not sonorous.
- Non-metals do not conduct electricity.
As we can see from these properties that non-metals are not lustrous, this means that they do not have the property to reflect light from their surface which we see as a shiny surface. This is due to the absence of free electrons in non-metals. While metals that have a property to contain free electrons can impart shine and are called lustrous.
However, there are certain exceptions in non-metals being non- lustrous. There are certain non-metals that are shiny in nature and can be termed as lustrous non- metals.
Some of the known non- metals that are lustrous in nature are, diamond, iodine, and graphite, etc.
Iodine is lustrous because of its large size. The force between outer electrons and the atom decreases due its size, so the outer electrons absorb heat and become excited, when this heat is released they seem to be shiny.
Diamond, a non- metal is considered to be lustrous due to its structure. The prism structure, and the angles of the carbon atoms, makes it reflect light and appear to be lustrous.
Hence, iodine, and diamond are some lustrous non-metals.

Note: Diamond and graphite are known to be allotropes of non- metal carbon, but they have some properties similar to metals, like graphite conducts electricity, and both diamond and graphite are lustrous due their structural position.