Question

The color of chlorine gas is
(A) Yellow
(B) Greenish yellow
(C) Pink
(D) Purple

Answer 1

Hint: Chlorine gas is represented by the formula $C{{l}_{2}}$. The atomic number of chlorine is 17 in the periodic table. Chlorine gas is abundant in nature and poisonous to most organic life. Chlorine gas is used in cleaning products.

Complete step by step answer:
To answer this question we will try to understand why chlorine gas is called ‘Chlorine’.

The word ‘Chloro’ means green, usually pale green. Pale green colour is different from normal green colour as it has a little yellowish gradient in it.
Chlorosis is the yellowing of plants. This means that the plant eventually loses its natural green colour and starts becoming yellow in colour. Now, in the word, ‘Chlorine’ we can see that it is derived from the word ‘Chlor’ which means that chlorine gas is pale green as well as yellowish in colour.
So, from the above discussion we can conclude that the colour of chlorine gas is greenish yellow.

Hence option (B) greenish-yellow is the correct answer.

Additional Information:
Lets see why chlorine gas have a greenish yellow color :
> In the chlorine atom. It has an outer electronic configuration of $3{{s}^{2}}3{{p}^{5}}$.
> It also has vacant 3d orbitals. So when the chlorine atom or molecule comes in contact with sunlight its electrons get transferred to vacant 3d orbitals.
> When the electrons return to their original shell they liberate that extra energy in the form of electromagnetic radiation. Given by formula $E=\dfrac{h}{\lambda }$. Here E is energy, h is Planck's constant, $\lambda $ is the wavelength of light.
> At room temperature in sunlight, the electron acquires energy from only green light. But if it's hot it will appear yellow.
This can be simply predicted by looking at the electromagnetic spectrum.

Note:
Don’t get confused between the color yellow and greenish yellow, sometimes chlorine gas may look yellow but the color of chlorine gas is greenish yellow. This yellow colouration of chlorine is because of the prolonged chlorosis of the chlorine gas. Freshly prepared chlorine gas is greenish-yellow colour.