Coloured Problem: Unpaired Electrons in Transition Metal Ions

  • Thread starter Ahmed Abdullah
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In summary, transition metal ions have unpaired electrons in the outermost shell of the d and f orbitals that absorb a particular wavelength of visible light and reflect the complementary wavelength, giving the substance its color. When the electrons return to their ground state, they emit light of the previously absorbed wavelength. This can result in a mixture of colors, making it appear white to the human eye. However, there may be other mechanisms besides photon absorption and emission that can cause changes in electron energy levels, leading to different photon-matter interactions and potentially altering the substance's color. Further research is needed to fully understand these processes.
  • #1
Ahmed Abdullah
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Coloured Problem!

We know that transition metal ions have unpaired electrons in the outermost shell of the d and f orbitals.
These unpaired electrons absorb a particular wavelength from visible light and are promoted to higher energy levels. Thus they reflect light of complement wavelength of the absorbed wavelength.
If the incoming light is white(containing light of all wavelength) and the ion absorbs green light for instance then it would reflect a mixture of red and blue wavlength (i.e. magenta).
Our eye recongnize the substance as magenta couloured.
When the electrons come back to ground state, they would emit light of the wavelength previously absorbed(i.e green here). Here I am confused. What the compound would look like? Green or magenta?
Here how I think about the problem.
We can resonably assume that the lattice of the substance is composed of a large number of ions. At any instance of time some electrons will absorb light and some other will emit light. Then some portion of the substance would look green and other portion magenta. If both of this happen million of times in a tiny area we will not able to detect distinct colour, rather things will mix up and overally we should see white colour.

I know there is some flaw in my analysis! What are the flaws?

Another question:
Is the exitation and de-exitation of electrons (quantum jump from one orbital to other) is the only reason that gives the subtances the colours they have?
Does compound other than transition metal have colour?

Your sensible answer will broad my understanding.
Thanks in advance.
 
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  • #2
There are things going on in materials that convert light energy into other forms of energy, particularly vibrational modes that are manifestations of heat energy

http://www.glenbrook.k12.il.us/gbssci/phys/Class/light/u12l2c.html

Not all of the light energy that is absorbed is stored in the higher electronic energy levels, so it is not released back into the universe as photons.
 
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  • #3
So does it means that electrons can store energy without promoting to higher electronic energy levels, and they are able to store energy (such as vibrational energy) as they remain in the same energy level.
 
  • #4
Ahmed Abdullah said:
So does it means that electrons can store energy without promoting to higher electronic energy levels, and they are able to store energy (such as vibrational energy) as they remain in the same energy level.

Electrons do not store energy without being promoted. If they could, we would probably not observe quantum phenomena. The electrons that absorb photons are promoted to higher electronic levels, but they do not necessarily release that energy as photons or as photons of the same energy that they absorbed. There are other mechanisms whereby an electron can lose its energy besides returning to the state from which it was promoted. It is also possible for them to gain energy (be promoted to a higher state) by mechanisms other than photon absorption. A gas discharge tube absorbs energy from electron collisions and releases that energy as photons with the characteristic frequencies associated with the electron transitions.

There are many possible photon-matter interactions besides the one you initially described of a single photon being absorbed, promoting an electron to a higher state, and then a photon of the same frequency being generated by an electron transition back to its original state. You might not find a satisfying single article on the subject, but if you search for non-radiative transitions you will at least find some indication of the many possibilities.
 

Related to Coloured Problem: Unpaired Electrons in Transition Metal Ions

1. What is the coloured problem in transition metal ions?

The coloured problem in transition metal ions refers to the phenomenon of these ions exhibiting different colors in solution or solid state. This is caused by unpaired electrons in the d-orbitals of the transition metal, which absorb and reflect certain wavelengths of light, resulting in the perceived color.

2. How do transition metal ions acquire unpaired electrons?

Transition metal ions acquire unpaired electrons through the process of losing electrons to form positively charged ions. This can occur through reactions with other atoms or molecules, or through the transfer of electrons during redox reactions.

3. Why do some transition metal ions have more unpaired electrons than others?

The number of unpaired electrons in transition metal ions depends on the electronic configuration of the ion. This is determined by the number of electrons in the d-orbitals of the transition metal and can vary depending on the atomic structure and chemical bonding of the ion.

4. How does the presence of unpaired electrons affect the chemical properties of transition metal ions?

The presence of unpaired electrons in transition metal ions makes them more reactive and able to form complex compounds. This is due to the ability of these electrons to participate in bonding with other atoms or molecules, resulting in a wide range of chemical properties and behaviors.

5. What applications does the coloured problem in transition metal ions have in science and technology?

The coloured problem in transition metal ions has a variety of applications in fields such as chemistry, biology, and materials science. It is used to study and understand the electronic and chemical properties of transition metal ions, as well as in the development of new materials and technologies such as dyes, pigments, and catalysts.

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