Question

Generally non-metals are not lustrous. Which of the following non-metal is lustrous?
A) Sulphur
B) Oxygen
C) Nitrogen
D) Iodine

Answer 1

Hint: The property of elements that shows how well the element reflects light is known as lustre.
Lustre is shown by solid surfaces when they reflect incident light. This is because of the presence of free electrons.

Complete answer:
The lustrous nature is exhibited by elements due to the presence of free electrons. In the periodic table, as we move down in the group, the size of the atoms increases. As the atomic size increases, more shells get added around the nucleus. As a result, the effective nuclear charge decreases and the electrons are loosely bound. Metals are lustrous but generally Non-metals are not lustrous i.e. they do not have a shiny appearance. Two non-metals are exceptions to this.
Many non-metals are not solid in nature.
An exception to this property is iodine. The atomic number of iodine is 53. Thus, iodine has a large atomic size. As a result, the effective nuclear charge experienced by the valence electrons is very low. Thus, the electrons in an iodine atom are loosely bound. Thus, iodine is lustrous.

Thus, the correct option is (D) iodine.

Additional Information Another non-metal that is lustrous is diamond. Diamond is an allotrope of carbon.

Note: Sulphur, oxygen and nitrogen have smaller atomic sizes. As a result, the electrons of sulphur, oxygen and nitrogen experience a strong effective nuclear charge. The electrons of sulphur, oxygen and nitrogen are not loosely bound and are not free. Thus, sulphur, oxygen and nitrogen are not lustrous.