Question

In the laboratory, sodium chloride is made by burning the sodium in the atmosphere of chlorine which is yellow in colour. The cause of yellow colour is
A) Presence of sodium ions in the crystal lattice
B) Presence of chloride ions in the crystal lattice
C) Presence of electron in the crystal lattice
D) Presence of face centred cubic crystal lattice

Answer 1

Hint: The colour in any compound is formed due to excitation of electrons from a low energy level to higher energy level. When the electron comes back to the low energy level it gives energy in forms of some colour in the visible range.

Complete Step by Step Answer:
Sodium chloride is a crystal of sodium ion and chloride ion. In this crystal sometimes some cation and anion is removed to form vacant sites in the crystal.

When the chloride ion is removed from the crystal it causes a vacant site. This is called the F-centre. This vacant site of the crystal is fulfilled by the higher energetic electrons. These electrons lie in the excited state. Thus when the electron jumps back to the ground state it shows yellow colour in the visible range.

Thus we can write that in the laboratory, sodium chloride is made by burning the sodium in the atmosphere of chlorine which is yellow in colour. The cause of yellow colour is due to the presence of electrons in the crystal lattice.
Thus the correct option is C.

Note: The production of sodium chloride from sodium atoms in the atmosphere of chlorine gas is done in a certain temperature and pressure. If we apply high temperatures in this process then no product is produced.