Question

Explain why:
Halogens are coloured and the colour deepens on moving down in the group from fluorine to iodine.

Answer 1

Hint:We must be wondering from where the name halogens come from so it is basically the salt producing ones. Further it is interesting to note here that the halogens are coloured because of their low ionisation energy which further let the electrons to get excited by absorbing the visible region of the light.

Complete answer:
 Firstly we will discuss the halogens so basically the halogens are found in the seventeen group of the periodic table. We must be wondering from where the name halogens come from so it is basically the salt producing ones. So we can say that when the halogens react with metals it produces the salt. Further we should know that the halogens are coloured. Further it is interesting to note here that the halogens are coloured because of their low ionisation energy which further let the electrons to get excited by absorbing the visible region of the light. As we know that the ionisation energy is the minimum amount of energy required to remove the loosely bound electron of an isolated neutral gas molecule and atoms. Moreover the reflected light thus imparts the complimentary colour to the molecule. As we move in the periodic table that is from the fluorine to iodine we come to know that the atomic radii increases, and this further concludes that the energy levels become closer and the low energy light as here we can say that the higher wavelength is directed towards the red. This is further absorbed and colour deepens on moving down the group.

Note:
We should know that the halogen group in the periodic table is only one in which the elements exist in three states of the matter at standard temperature and pressure. By absorbing light the electrons get excited and this further leads to the deepening in the colour on moving down the group.