Direction (Q. No. 25) This section is based on Statement I and Stateme...
Halogen molecule absorbs light in the visible region as a result of which their electrons are excited to higher energy level while the remaining light is transmitted.
The colour of halogens is actually the colour of this transmitted light, i.e. halogens have complementary colours.
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Direction (Q. No. 25) This section is based on Statement I and Stateme...
Statement I: All halogens are coloured.
All halogens, which include fluorine, chlorine, bromine, iodine, and astatine, are indeed coloured. This means that they have distinct colours when they are in their elemental form or as compounds. For example, fluorine gas is a pale yellow color, chlorine gas is greenish-yellow, bromine is reddish-brown, iodine is violet, and astatine is black.
Statement II: Halogens absorb part of the light in the visible region.
This statement is also correct. Halogens have a unique electronic configuration that allows them to absorb certain wavelengths of light in the visible region. When light passes through or interacts with a halogen, some of the wavelengths are absorbed, while others are reflected or transmitted. The absorbed wavelengths correspond to the colors that we perceive.
Explanation:
The reason why halogens are coloured is directly related to their electronic structure. Halogens have seven valence electrons in their outermost energy level. When they form compounds, they tend to gain one electron to achieve a stable octet configuration. This electron gain results in the formation of negatively charged ions called halides.
The absorption of light by halogens occurs due to the presence of unpaired electrons in their outermost energy level. These unpaired electrons can absorb photons of specific energies, corresponding to specific wavelengths in the visible region. The absorbed energy causes the electrons to move to higher energy levels or transition to different orbitals. This transition results in the absorption of certain colors of light and the reflection or transmission of others, giving rise to the observed color of the halogen or its compounds.
For example, chlorine gas appears greenish-yellow because it absorbs light in the blue region of the spectrum. The absorbed blue light corresponds to a specific energy level transition in the chlorine atoms. The remaining green and yellow wavelengths are reflected or transmitted, giving the characteristic color. Similar principles apply to other halogens, with each exhibiting a unique color due to the specific energy transitions associated with their electronic structure.
In conclusion, both Statement I and Statement II are correct, and Statement II provides the correct explanation for why halogens are coloured. The absorption of light in the visible region by halogens is directly related to their electronic structure and the presence of unpaired electrons.