Question

Which of the following is a lustrous non-metal?
(A) Chlorine
(B) Nitrogen
(C) Iodine
(D) Florine

Answer 1

Hint: Non metals are non lustrous in nature, with the exception of two elements. So the answer to the question lies in the exception.

Complete step by step answer:
> Lustre is the property of minerals that shows how much or how well the mineral reflects light. Lustre has two categories: metallic and non-metallic.
> Most of the nonmetals are not solid and do not have any crystalline surface. Normally lustre is shown by the surface of a solid by reflecting an incident light. Since the non metals do not meet this condition they do not show lustre.
> However there is an exception. Two of the non metals show lustre they are diamond and Iodine.
So we can conclude that Iodine is a lustrous non-metal. Therefore, Option C is the correct answer.

Additional Information:
> Screening effect is also known as the shielding effect. The phenomenon which occurs when the nucleus reduces its force of attraction on the valence electrons, due to the presence of electrons in the inner shell is known as a screening effect.
> The atomic number of iodine is 53. Iodine is the fourth element in the seventeenth column of the periodic table.
> Iodine has 7 valence electrons in the outer shell.

Note: Luster is basically due to free electrons. As we move down the group, the size of the atoms increases and more shells are added. So due to screening effect, effective nuclear charge is less and hence electrons are loosely bound. Therefore iodine is lustrous.